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IC     STATE    UNIVERSITY      OH     HILl     L    BR 


S00281793  U 


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This  book  is  due  on  the  date  indicated 
below  and  is  subject  to  an  overdue  fine 
as  posted  at  the  Circulation  Desk. 


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31 
-  2  1987 

LABORATORY  AND  FIELD 
MANUAL  OF  BOTANY 


BY 


JOSEPH  Y.  BERGEN,  A.M. 

Author  of  "  Elements  of  Botany,"  "  Foundations  of  Botany, 
"  Primer  of  Darwinism,"  etc.      ' 


AND 

BRADLEY  M.  DAVIS,  Ph.D. 

Professob  of  Botany  in  the  University  of  Pknnsvt >v axta 


GINN  AND  COMPANY 

BOSTON     •    NEW   YORK     •    CHICAGO     •    LONDON 
ATLANTA    •    DALLAS    •    COLUMBUS    •    SAN   FRANCLSCO 


Copyright,  1907,  by 
(Joseph  Y.  Bergkn  and  Bradley  M.  Davis 


ALL  RIGHTS  RESERVED 
716.10 


CINN  A.\n  COMl'AXV  •  PRO- 
PRIETORS •  ROS TON  •  U.S.A. 


PREFACE 


This  manual  offers  material  for  much  more  than  a  year's 
laboratory  work.  This  is  made  necessary  by  the  fact  that  in- 
structors differ  widely  in  their  views  as  to  what  matter  should 
be  presented  in  an  introductory  course  under  the  variety  of 
conditions  obtaining  where  botany  is  taught.  •  A  course  must 
necessarily  be  framed  selectively,  and  the  chief  alternatives  are 
discussed  in  the  opening  paragraphs  of  the  Introduction. 

The  authors  fully  recognize  the  fact  that  no  set  of  directions 
of  only  moderate  fullness  can  tell  the  student  all  that  he  needs 
to  know  aboult  choice  of  material,  apparatus,  and  manipulation. 
It  is  assumed  that  much  is  left  to  be  explained  by  the  instructor, 
and  constant  mention  is  made  of  general  and  special  laboratory 
guides  which  may  be  consulted  for  needed  details. 

The  student  in  the  laboratory  is  not  to  consider  himself  as 
merely  the  corroborator  of  facts  already  ascertained  :  he  is  to 
interrogate  mainly  not  the  instructor,  not  the  manual,  but  the 
plant  itself.  The  directions  here  given  are,  therefore,  for  the 
most  part  suggestions  on  methods  of  procedure  and  indications 
as  to  the  plants  or  parts  of  plants  in  which  to  look  for  desired 
information. 

Since  the  amount  of  ground  that  can  be  covered  by  labora- 
tory divisions  varies  so  largely  with  many  circumstances,  it  has 
seemed  desirable  to  designate  two  courses,  a  briefer  and  a  fuller 
one.  The  matter  which  may  be  omitted  from  the  latter  to  frame 
the  shorter  course  is  printed  in  smaller  type  and  consists  in  the 
main  of  rather  more  difficult  or  detailed  studies  than  those  which 
appear  in  the  larger  type.  In  a  general  way  the  order  of  treat- 
ment follows  that  of  the  authors'  Principles  of  Botany ^  but  the 


iv  PREFACE 

sliorter  course  does  not  cover  many  more  topics  than  are  dealt 
with  in  Bergen's  Elements  or  Foundations  of  Botany,  and  may  be 
used  with  either  of  those  books. 

Part  I  consists  mainly  of  studies  on  the  gross  anatomy  and 
tlie  histology  of  seed  plants,  together  with  a  set  of  separately 
numbered  experiments  to  illustrate  some  of  the  main  principles 
of  plant  physiology. 

Part  II  deals  Avith  type  studies  of  spore  plants,  outlining  the 
evolution  and  classification  of  the  plant  kingdom.  Here  will  also 
be  found  studies  on  the  gametophyte  phases  and  the  life  histories 
of  seed  plants  to  show  their  relationships  to  the  spore  plants. 
Part  II  is  introduced  by  outlines  on  the  plant  cell  to  illustrate 
the  chief  principles  of  growth  and  reproduction. 

Part  III  is  concerned  with  a  series  of  laboratory  and  field 
studies  which  may  serve  to  offer  at  least  an  outline  for  the 
treatment  of  ecology  as  a  scientific  subject.  Profound  ecological 
studies  demand  far  more  knowledge  of  taxonomy,  plant  phys- 
iology, meteorology,  the  physics  and  chemistry  of  soils,  and 
kindred  subjects  than  can  be  required  of  beginners  in  botany. 
However,  the  authors  believe  that  it  is  quite  possible  to  illustrate, 
even  to  beginners,  something  of  the  kind  of  quantitative  discus- 
sion of  variations  in  environment  and  the  responses  of  plants 
to  changed  conditions,  which  must  distinguish  the  ecology  of 
the  future. 

Hearty  acknowledgments  for  valuable  suggestions  are  due  to 
A.  T.  Bell,  F.  E.  Clements,  W.  N.  Olute,  W.  F.  Ganong,  B.  Gruen- 
berg.  Miss  Lillian  J.  MacRae,  G.  J.  Peirce,  and  R.  B.  Wylie,  who 
liave  wholly  or  in  part  read  the  manuscript  or  the  proofs. 

J.  Y.  B. 

('AMHKiiKiE,  March,  1907  ^    ^i   j) 


CONTENTS 


INTRODUCTION 

LABORATORY  METHODS  AND  EQUIPMENT 


Page 
1 


PART  I  — STRUCTURE  AND  PHYSIOLOGY  OF  SEED  PLANTS 

Introductory  Study  of  a  Seed  Plant  and  its  Organs         .         .         .         ,15 

The  Seed  and  its  Germination 17 

Storage  of  Food  in  the  Seed 21 

Movements,  Development,  and  Morphology  of  the  Seedling  .         .         .27 

Roots 29 

Some  Properties  of  Cells  and  their  Functions  in  the  Root       .        .         .  oG 

Stems 87 

Structure  of  the  Stem 30 

Work  of  the  Stem 45 

Buds 48 

Leaves 51 

Leaf  Arrangement  with  Reference  to  Light 53 

Minute  Structure  and  Functions  of  Leaves 55 

The  Flower  of  the  Higher  Seed  Plants 64 

Pollination  and  Fertilization 68 

The  Fruit 69 


PART  II  — TYPE  STUDIES  PRECEDED  BY  THE  STUDY 
OF  THE  PLANT  CELL 


The  Plant  Cell,  its  Structure  and  Reproduction 

The  Flagellates,  or  Flagellata 

The  Sliuie  Molds,  or  Myxomycetes 

The  Blue-Green  Alg«,  or  Cyanophycese 

The  Green  Alg?e,  or  Chlorophycese 

The  Brown  Algffi,  or  Phgeophyceae  . 

The  Red  Algse,  or  Rhodophyceaj     . 

The  Bacteria,  or  Schizomycetes 

The  Yeasts,  or  Saccharomycetes     . 

The  Alga-like  Fungi,  or  P'hyco'myceres 


75 

83 

83 

84 

87 

97 

100 

102 

105 

107 


VI 


CONTENTS 

Page 

The  Sac  Fungi,  or  Ascomycetcs HO 

The  Lichens 112 

The  Basidia  Fungi,  or  Basidiomycetes 114 

The  Liverworts,  or  Ilepatica; H" 

The  Mosses,  or  Musci 126 

The  Ferns,  or  Filicinese 132 

The  Horsetails,  or  Equisetinese 142 

The  Club  Mosses,  or  Lycopodineae 145 

The  Gymnosperms,  or  Gymnospermce 151 

The  Angiosperms,  or  Angiospermse 159 


PART  III  — ECOLOGY 


Parasitic  and  Carnivorous  Plants    . 
How  Plants  protect  themselves  from  Animals 
Pollination  of  Flowers     .... 
How  Plants  are  scattered  and  propagated 
Competition  and  Invasion 

Plant  Successions 

Ecological  Classes 

Plant  Formations  ;  Zonation  . 
Study  of  Types  of  Seed  Plants 


167 

168 
168 
172 
174 
175 
175 
177 
179 


BOTANICAL  MICROTECHNIQUE 

General  Reagents  employed  in  Temporary  Preparations         .         .         .  188 
Some  Special  Reagents  for  Microchemical  Tests  and  Temporary  Prepa- 
rations     ............  190 

Killing  and  Fixing  ...........  191 

The  Preservation  of  Material 195 

General  Staining  Methods 197 

Mounting  in  Balsam  and  Glycerin  .......  200 

Imbedding  in  Paraffin      ..........  202 

Sectioning 204 

Staining  on  the  Slide 207 

CULTURE  METHODS 

The  Culture  of  Algje 211 

The  Culture  of  Fungi 212 

The  Culture  of  Liverworts  and  Mosses 215 

The  Culture  of  Ferns 216 

The  Culture  of  Seed  Plants 216 


CONTENTS 

MATERIAL,   APPARATUS,   AND  SUPPLIES 

Lists  of  Preparations  for  the  Microscope  .... 

Suggestions  on  Material  for  the  Study  of  Plant  Histology 

Apparatus  for  the  Laboratory 

Chemicals  for  the  Laboratory 

Dealers  in  Material,  Apparatus,  and  Supplies 


vu 


Page 
.  217 
.  220 
.  222 
.  224 
.  225 


BIBLIOGRAPHY 227 

APPENDIX 2^^ 

GLOSSARY 2^^ 

INDEX 2^^ 


LIST   OF  EXPERIMENTS 


I.    Temperature  and  germination 
II.    Amount  of  water  in  seeds 

III.  Relation  of  air  to  germination 

IV.  Effect  of  germination  on  air    . 
V.    Use  of  the  pea  cotyledons  after  germination 

VI.    Relation  of  food  in  seed  to  rate  of  growth 
VII.    Occurrence  of  starch  in  seeds 
VIII.    Oil  in  flaxseed  .         .         •         •         • 

IX.    Proteids  in  seeds 

X.    Plant  foods  in  Brazil  nuts 
XI.    Cause  of  arch  of  hypocotyl      . 
XII.    Discrimination  between  root  and  hypocotyl 

XIII.  Growing  region  of  root    .... 

XIV.  Percentage  of  water  in  the  plant  body    . 
XV.    Water  cultures 

XVI.    Root  absorption  with  diminished  temperature 
XVII.    Region  of  bending  in  the  root 
XVIII.    Pressure  of  root  tip  .... 

XIX.    Cause  of  downward  growth  of  root 

XX.   Osmosis 

XXI.    Osmosis  of  Begonia  leaf  .... 
XXII.    Course  of  water  in  stems 

XXIII.  Relation  of  loss  of  water  to  firmness  of  tissues 

XXIV.  Use  of  cork 


Page 

.  19 

.  20 

.  21 

.  21 

.  21 

.  22 

.  24 

.  25 

.  26 

.  26 

.  27 

.  28 

.  28 

.  33 

.  33 

.  34 

.  35 

.  35 

.  36 

.  36 

.  37 

.  45 

.  46 

.  47 


VIU 

XXV. 

XXVI. 

XXVII. 

XXVIII. 

XXIX. 

XXX. 

XXXI. 

XXXII. 

XXXIII. 

XXXIV. 

XXXV. 

XXXVI. 

XXXVII. 

XXXVIII. 

XXXIX. 

XL. 

XLI. 

XLII. 


CONTENTS 

Reserve  sugar  in  onion  bulb 

Proteids  in  onion  bulb 

Cause  of  nocturnal  position  of  leaves  .... 
Values  of  illumination  for  leaf  positions 
Adaptation  of  growing  leaves  to  changed  light  relations 
Heliotropic  movements  of  English  ivy 


Pagb 
.  48 
.  48 
.  53 
.  53 
.  54 
.     55 


Oxygen  making  by  plants 57 

Starch  in  Tropceolum  leaves 57 

Consumption  of  starch  in  Tropmolum  leaves  .  .  .58 
Effect  of  sealing  stomata  on  starch  production  .  .  .59 
Effect  of  darkness  on  chlorophyll  production       .  ^       .         .69 

Transpiration 60 

Side  of  Ficus  elastica  leaf  which  transpires  .         .         .61 

Relative  transpiration  of  Hydrangea  Hortensia  and  Ficus 

elastica 61 

Passage  of  water  from  stem  to  leaf 63 

Rise  of  water  in  leaves 63 

Starch  contents  of  leaves  at  various  seasons  .  .  .63 
Production  of  pollen  tubes 68 


LABOEATOEY  AND  FIELD 
MANUAL  OF  BOTANY 

INTRODUCTION 

It  is  intended  that  these  laboratory  outlines  shall  be  found 
adaptable  to  several  methods  of  approach  in  framing  a  general 
course  in  elementary  botany. 

First.  By  beginning  with  Part  I  the  student  may  consider  first 
the  more  general  features  of  the  morphology  of  the  seed  plant 
and  the  most  important  of  its  physiological  activities.  This 
may  then  be  followed  by  studies  of  a  series  of  spore  plants 
(Part  II),  to  outline  the  chief  steps  in  plant  evolution.  Such  work 
as  is  possible  in  plant  ecology  (Part  III)  is  thus  deferred  to  the 
end  of  the  course. 

Second.  By  commencing  with  Part  II  the  student  will  be 
introduced  at  once  to  the  principles  of  cell  structure,  growth,  and 
reproduction,  and  can  then  trace  the  evolution  of  the  plant  king- 
dom. By  this  arrangement  selections  from  Part  I  will  follow  the 
studies  of  Part  II,  and  Part  III  will  receive  attention  last. 

Third.  Part  I  may  be  followed  at  once  by  Part  III,  and  the 
studies  of  Part  II  be  used  only  to  illustrate  such  types  and  topics 
concerned  with  spore  plants  as  may  seem  desirable. 

Fourth.  It  is  by  no  means  necessary  that  the  matter  of  Part  I 
be  taken  up  in  the  order  given.  Instead  of  beginning  with  the 
plant  as  a  whole  or  with  the  seed,  a  course  may  be  readily  shaped 
so  as  to  commence  with  the  fruit  or  with  the  leaf. 

The  planning  of  a  course  depends  upon  so  many  factors,  such  as 
season,  material,  equipment,  maturity  of  students,  and  the  time 

1 


2  INTRODUCTION 

at  the  disposal  of  the  class,  that  it  must  vary  greatly  with  the 
different  conditions.  The  authors,  recognizing  these  difficulties, 
have  tried  to  present  a  flexible  outline  in  a  thoroughly  practical 
manual  containing  sufficient  material  to  permit  of  a  wide  range 
of  choice.  In  general  they  believe  that  the  best  results  wdll 
be  obtained,  when  a  full  year  can  be  devoted  to  the  subject,  by 
taking  the  matter  in  the  order  given  in  the  first  or  second  of 
the  alternatives  presented  above.  If  only  a  half  year  is  avail- 
able, the  best  course  in  their  judgment  is  that  indicated  in  the 
third  alternative. 

For  the  guidance  of  any  who  niaij  care  for  such  suggestions  the 
authors  have  designated  hij  double  asterisks  (**)  those  experiments 
and  studies  which  the//  consider  to  he  the  most  valuable. 

A  brief  discussion  of  laboratory  methods  and  equipment  is 
presented  immediately  before  the  laboratory  outlines  and  experi- 
ments of  Parts  I,  II,  and  III.  It  is  hoped  that  the  instructor  may 
find  some  helpful  suggestions  in  this,  and  certain  parts  are 
written  expressly  to  aid  the  student  to  an  understanding  of  the 
spirit  ( of  laboratory  work,  methods  of  drawing,  note  taking,  and 
the  care  of  instruments. 

The  essential  methods  of  botanical  microtechnique  and  the 
preparation  of  the  material  are  taken  up  after  the  laboratory  out- 
lines. This  account  has  been  introduced  to  assist  the  instructor 
and  the  advanced  student  in  the  collection  and  preservation  of 
material  and  in  the  more  detailed  studies  of  plant  histology  and 
cytology,  which  demand  the  preparation  of  microtome  sections 
and  critical  staining  methods.  The  discussion  does  not  attempt 
to  give  such  details  covering  special  studies  as  may  be  found  in 
several  more  exhaustive  treatises  to  which  the  reader  will  be 
referred.  It  endeavors  rather  to  outline  standard  methods  of 
killing,  fixing,  preserving,  cutting,  and  staining  plant  structures, 
which  cannot  fail  to  give  good  results,  with  the  reasons  why 
they  have  been  selected.  Some  simple  directions  for  the  culture 
of  alg£e,  fungi,  moss  protonema,  fern  prothallia,  etc.,  follow  the 
account  of  microtechnique. 


INTRODUCTION  3 

A  section  entitled  ''  Material,  Apparatus,  and  Supplies  "  gives 
lists  of  preparations  for  the  microscope,  favorable  material  for 
histological  work,  apparatus  and  supplies,  with  the  addresses  of 
dealers  who  furnish  these  to  the  trade. 

The  bibliography  has  been  chosen  with  the  purpose  of  present- 
ing a  group  of  books  many  of  which  are  within  the  possibilities 
even  of  a  well-equipped  school  library,  rather  than  a  lengthy  list 
of  detailed  literature  which  is  usually  only  handled  by  the  spe- 
cialist. These  works  are  numbered  and  the  references  to  them 
throughout  the  manual  will  be  by  the  author's  name  and  the 
number. 

An  appendix  with  suggestions  to  instructors  follows  the  bibliog- 
raphy. This  contains  matter  which  it  is  not  necessary  for  the 
student  to  read  in  connection  with  his  laboratory  work,  although 
in  many  cases  it  may  be  of  interest  for  him  to  do  so.  The  ap- 
pendix is  really  a  collection  of  practical  notes  based  on  the 
experience  of  the  authors  or  gathered  from  conversations  and 
correspondence  with  many  teachers.  Indeed,  it  is  a  feature  which 
the  authors  have  introduced  in  the  hope  that  it  may  bring  forth 
other  helpful  and  practical  suggestions  from  those  who  use  the 
book,  and  correspondence  upon  this  subject  is  cordially  invited. 

A  glossary  gives  a  selected  list  of  botanical  terms,  including 
the  most  important  of  those  used  in  this  manual  and  in  the 
authors'  Principles  of  Botany. 

Only  a  few  necessary  abbreviations  have  been  used,  to  econo- 
mize space.  As  stated  above,  books  listed  in  the  bibliography 
are  referred  to  by  the  author's  name  and  number  in  the  list. 
Pi'inciples  designates  the  Principles  of  Botany  ;  App.,  the  ap- 
pendix ;  l.p.,  m.p.,  and  h.p.  refer  to  low  power,  medium  power, 
and  high  power  of  the  compound  microscope  respectively ;  lens 
means  either  hand  lens  or  dissecting  microscope  as  the  case  may 
be ;  c.p.  means  chemically  pure.  The  usual  abbreviations  for 
the  units  of  the  metric  system  are  frequently  employed. 


LABORATORY  METHODS  AND  EQUIPMENT 
The  Laboratory  and  its  Equipment 

The  essentials  of  a  laboratory  are,  of  course,  good  light,  con- 
venient tables,  and  sufficient  apparatus.  While  north  light  is 
preferable,  since  its  quality  is  more  constant,  east,  west,  or  south 
light  can  be  perfectly  regulated  by  translucent  shades  wliich  may 
be  pulled  up  to  any  desired  distance,  and  so  temper  direct  sun- 
light when  necessary.  Moreover,  it  is  desirable  that  some  win- 
dows have  the  sun  for  part  of  the  day,  since  aquaria  and  glass' 
cases  for  growing  plants  require  some  sunlight  and  may  be  placed 
in  such  parts  of  the  room.  Excellent  suggestions  on  the  arrange- 
ment of  laboratory  tables,  lockers,  glass  growing  case,  sink,  black- 
board, etc.,  are  given  in  Ganong,  7,  Chapter  V,  and  in  Lloyd,  8, 
Chapter  IX,  books  which  should  be  read  by  every  teacher  of  botany. 

The  equipment  of  a  laboratory  will  depend  largely  upon  the 
nature  of  the  work,  whether  very  elementary  or  covering  a  strong 
full  course  of  a  year  or  more,  and  also  upon  the  attitude  of  the 
instructor,  who  may  emphasize  especially  either  physiology  or  a 
more  detailed  morphology.  Physiology  requires  its  own  special 
apparatus,  and  detailed  morphology  demands  the  equipment 
necessary  for  imbedding,  microtome  section  cutting,  and  staining. 
Much  of  the  work  with  this  apparatus  can  best  be  conducted  at 
tables  in  the  center  or  back  of  the  laboratory,  which  will  not 
interfere  with  the  tables  for  the  more  general  class  exercises.  In 
the  choice  of  equipment  and  its  storage  the  instructor  is  again 
referred  to  the  admirable  discussions  of  Ganong  and  Lloyd. 
Lists  of  the  chemicals,  apparatus,  and  supplies  necessary  for  the 
work  outlined  in  this  manual  are  given  in  Sees.  215,  216. 

The  cost  of  compound  microscopes  is  the  item  of  greatest 
expense  in  the  equipment  of  a  laboratory,  and  their  selection 

4 


GKOWING   PLANTS  IN  THE  LABORATORY  5 

tleraaiids  careful  thought.  The  laboratory  should  have  enough 
microscopes  so  that  every  student  in  a  section  may  have  his  own 
instrument.  If  this  is  not  possible,  it  is  better  that  the  course 
should  be  planned  along  such  lines  that  the  microscopic  work 
is  largely  in  the  nature  of  demonstrations  by  the  instructor 
on  such  microscopes  as  are  available.  Two  or  three  students 
working  together  at  the  same  microscope  create  confusion  and 
secure  poor  results.  There  are  a  number  of  medium-priced  instru- 
ments on  the  market,  with  varying  merits,  from  wliich  the 
instructor  must  choose  for  himself.  A  list  of  the  more  prominent 
firms  and  agents  is  given  in  Sec.  218.  It  is  false  economy  to 
attempt  to  save  expense  on  microscopes  at  the  cost  of  workman- 
ship and  convenience  in  form.  A  set  of  microscopes  may  readily 
be  kept  on  the  laboratory  tables,  protected  from  the  dust  when 
not  in  use  by  paper  cones,  and  used  by  successive  sections, 
although  this  system  demands  much  more  watchfulness  on  the 
])art  of  the  instructor  than  when  each  student  has  his  own 
instrument  and  is  held  responsible  for  its  care. 

Growing  Plants  in  the  Laboratory 

Window  sills  and  unused  space  should  be  utilized  as  far  as 
possible  for  keeping  fresh  and  growing  material  alive  in  the 
laboratory,  not  only  for  the  interest  that  it  arouses  but  also  as 
a  practical  matter  of  foresight  which  at  times  saves  much  diffi- 
culty. Large  jars  covered  with  plate  glass  make  excellent  aquaria 
and  give  little  or  no  trouble.  A  surprising  number  of  forms 
will  appear  in  them  from  time  to  time,  and  very  interesting 
cultures  frequently  become  established.  A  glass  growing  case 
(Wardian  case)  such  as  is  described  by  Ganon(j,  7,  p.  82,  is  a 
most  useful  piece  of  equipment,  and  practically  indispensable 
for  much  physiological  work  when  conservatories  or  greenhouses 
are  not  available.  A  bay  window  shut  off  from  the  rest  of 
the  room  by  tight  glass  screens  is  better  still  if  the  heat  can 
be  regulated. 


6  LABORATORY   METHODS  AND  EQUIPMENT 

Laboratory  Material,  Preparations,  and 
Collections 

a  laboratory  should  be  kept  well  stocked  with  material  and 
slides  sufficient  for  its  work  so  that  the  instructor  is  never  at  a 
loss  for  them.  Some  material  and  slides  will  probably  have  to  be 
purchased,  and  a  list  of  dealers  in  botanical  supplies  is  given  in 
Sec.  217.  However,  very  many  instructors  will  depend  chiefly  on 
their  own  preparations  and  collections,  and  it  is  very  desirable 
that  they  do  so.  Material  collected  and  prepared  by  oneself  will 
be  generally  better  known  and  better  taught  than  that  from 
dealers.  The  secret  of  keeping  a  laboratory  well  stocked  is  the 
foresight  which  never  loses  the  opportunity  to  preserve  a  fortu- 
nate collection.  The  simpler  methods  of  killing  and  preserving 
material  are  given  in  Sec.  172.  There  are  no  great  difficulties  of 
technique,  and  it  is  the  experience  of  every  botanist  that  mate- 
rial will  come  to  hand  from  time  to  time  that  is  far  better  than 
the  average  of  that  offered  by  the  dealers.  A  laboratory  should 
always  have  large  bottles  of  stock  solutions  of  the  simpler  kill- 
ing reagents  (such  as  chrom-acetic  acid)  and  preserving  fluids 
(such  as  alcohol)  and  a  supply  of  wide-mouthed  bottles  and  jars. 
With  this  simple  equipment  at  hand  the  instructor  should  be 
constantly  on  the  watch  for  opportunities  to  increase  and  improve 
the  laboratory  stock.  Thoughtfulness  in  this  direction  will  save 
much  time  and  expense  in  the  long  run. 

It  is  becoming  desirable  and  even  necessary  to  study  many 
points  of  detailed  morphology  and  cell  structure  from  slides. 
These  can  be  purchased  singly  or  in  sets  from  dealers  (Sec.  217) 
and  the  preparations  are  generally  good  ;  however,  the  instructor 
is  urged  to  be  self-reliant.  The  simpler  methods  of  killing,  im- 
bedding, cutting,  and  staining  are  not  difficult  and  are  outlined 
in  the  sections  entitled  Botanical  Microtechnique.  An  advanced 
student  under  direction  can  profitably  be  employed  from  time  to 
time  in  the  service  of  slide  making  with  excellent  returns  for  the 
expenditure  involved.    But  more  important  is  the  added  value 


LABORATORY  METHODS  7 

of  working  with  material  that  is  thoroughly  familiar.  There  is 
danger  in  depending  too  much  on  slides,  and  they  should  not  be 
used  where  the  student  may  readily  make  temporary  prepara- 
tions, for  much  of  the  value  of  laboratory  work  lies  in  the  devel- 
opment in  the  student  of  a  certain  manual  skill.  It  is,  however, 
still  more  important  that  he  become  acquainted  with  and  study 
material  first-hand.  Botany  made  too  easy  by  doing  for  the  stu- 
dent what  he  can  do  for  himself  is  botany  robbed  of  certain  of 
•its  most  obvious  advantages  as  a  laboratory  study. 

Some  instructors  are  making  considerable  use  of  the  lantern 
and  photographs,  especially  to  illustrate  ecological  subjects,  and 
for  this  purpose  they  are  of  the  greatest  service.  Large  and 
varied  selections  of  lantern  slides  may  be  purchased  (Sec.  219). 
Charts  have  their  evident  value  and  there  are  some  excellent, 
although  expensive,  sets  published  (Sec.  219).  It  is  not  difficult 
to  make  simple  charts  and  diagrams  even  in  colors  {^Ganong,  7, 
p.  115),  and  these  may  be  adapted  to  the  particular  needs  of  the 
course  and  cost  almost  nothing. 

The  herbarium  and  museum  are  most  useful  adjuncts  to  the 
laboratory.  Especially  important  is  demonstration  material  of 
groups  which  cannot  be  studied  in  many  regions  from  living 
plants,  as,  for  example,  the  marine  algse.  Such  material,  either 
in  the  form  of  herbarium  sheets  or  on  exhibition  in  museum 
cases,  forms  a  most  useful  part  of  the  equipment  of  a  botanical 
department.  The  advantages  of  collections  covering  the  local 
flora  are  too  obvious  to  need  discussion.  These  matters  are  well 
treated  by  Ganong,  7,  Chapter  VI. 


Laboratory  Methods 

The  laboratory  work,  with  its  accompanying  notes,  should 
be  kept  absolutely  separate  from  the  text  reading.  Text-books 
should  not  be  allowed  on  the  laboratory  tables.  Their  function 
is  to  present  systematized  accounts  and  conclusions  after  the 
student  has  obtained  a  sufficient  first-hand  knowledge  of  the 


8  I.AP.OJLVTOUV    MHTllODS   AND   KQlIl'MENT 

facts  from  the  plants  themselves,  and  to  weld  into  one  systematic 
whole  the  somewhat  isolated  topics  of  laboratory  study.  Tt  is 
essential  to  good  laboratory  methods  that  the  drawing  and  writing 
of  notes  be  done  in  the  laboratory,  which  should  be  regarded  as 
a  study  room,  like  a  library,  open  to  the  student  as  many  hours 
of  the  day  as  is  possiWe,  and  every  encouragement  should  be 
t^iven  to  extended  individual  work. 


The  Labokatory  Equipment  of  Each  Student 

Every  student  should  have  an  individual  equipment,  kept 
either  in  the  drawers  of  the  table  or  in  lockers  at  the  side  of  the 
laboratory.  The  following  essential  instruments  and  supplies 
had  best  be  purchased  by  himself. 

1.  A  razor,  scalpel,  forceps,  and  pair  of  needles. 

2.  Slides  and  cover  glasses. 

3.  Tour  solid  watch  glasses  or  salt  dishes. 

4.  Two  pipettes  (medicine  droppers),  a  camel's-hair  brush, 
and  a  scale  in  centimeters,  millimeters,  and  inches. 

5.  A  medium  pencil  (4H)  or  two  pencils,  hard  (6H)  and  rather 
soft  (3H),  eraser,  mapping  pens,  liquid  India  ink,  red  ink,  and 
blue  ink.  Several  colored  pencils  will  be  found  very  useful  if  the 
student  is  to  construct  diagrams  illustrating  life  histories  and  other 
topics  (App.,  18).  Higgins'  red-label  India  ink  runs  more  smoothly 
and  is  generally  more  satisfactory  than  the  waterproof  ink. 

6.  Drawing  paper  and  notebook.  The  drawings  required  may 
be  made  on  loose  sheets  kept  in  a  folder,  and  the  notes  in  a 
book,  but  it  has  generally  proved  more  convenient  to  use  per- 
forated sheets  of  both  drawing  paper  and  note  paper,  cut  to  the 
same  size,  which  can  be  loosely  held  together  between  stiff  covers 
by  a  string.  Such  paper  can  be  purchased  in  blocks  from  certain 
dealers  (Sec.  218),  or  may  be  made  up  by  a  local  stationer.  The 
drawing  paper  should  take  ink  as  well  as  fine  pencil  lines. 

7.  A  hand  lens  is  necessary  unless  the  laboratory  tables  are 
supplied  with  simple  dissecting  microscopes. 


Ki:CC)lll)ING    NOTES  9 

There  should  always  be  a  general  supply  of  glass  tumblers, 
plates,  saucers,  etc.,  to  hold  material,  and  a  set  of  the  simpler 
reagents,  such  as  iodine,  eosin,  acetic  acid,  potash  solution, 
glycerin,  etc.  (Sees.  169,  170)  may  be  placed  on  each  table. 

General  Directions  for  the  Student  in  Draaving 
AND  Recording  Notes 

1.  Plan  your  drawings  so  that  every  sheet  covers  a  definite 
subject  or  part  of  a  subject  and  is  not  a  mixture  of  unrelated 
matter.  There  are  three  types  of  drawings,  habit  sketches, 
diagrams,  and  detailed  Jiyures,  which  should  never  be  coml)ined 
in  the  same  outline.  The  habit  sketch  and  diagrams  treat  of 
general  features,  usually  on  a  scale  which  makes  it  impossible 
to  show  details,  which,  if  included,  would  either  be  out  of  pro- 
portion and  inaccurate,  or  on  too  small  a  scale  to  be  of  value. 
Treat  the  drawings  as  a  form  of  expression  which  should  have 
the  characteristics  of  good  English,  —  namely,  simplicity,  clear- 
ness, and  accuracy. 

2.  Depend  chiefly  on  accurate  outlines.  Shade  as  little  as  pos- 
sible, and  then  simply  and  effectively  (see  Princqdes,  Figs.  8, 
20,  113,  134,  168,  247,  273,  299).  Do  not  put  in  details  which 
you  imagine  but  cannot  see.  Do  not  make  objects  appear  more 
geometrically  regular  than  they  really  are;  peas  are  not  per- 
fectly spherical,  pith  cells  seen  in  section  never  have  the  outlines 
of  perfect  hexagons,  and  so  on. 

3.  Group  your  figures  in  an  orderly  manner,  so  that  they  tell  a 
consecutive  story  on  the  page,  as  illustrated  in  the  Principles  by 
Figs.  8,  212,  270,  and  299. 

4.  Ink  drawings  are  more  durable  than  pencil,  but  the  manipu- 
lation requires  a  sure  touch  and  some  delicacy  of  treatment. 
They  are  best  preceded  by  light  pencil  outlines,  to  establish 
proportions,  which  may  be  erased  when  the  figure  is  finished. 
Use  an  India  ink,  diluted  if  necessary  with  weak  ammonia 
water  so  that  it  will  flow  smoothly.     Ink  drawings  are  worth 


10  LABOIIA TORY   METHODS   AND   KQUir^AIEXT 

trying   and    are   generally   favored  by   those  with   aptitude   for 
illustration. 

5.  Describe  the  figures  either  neatly  in  a  legend  at  the  bottom 
of  the  sheet  or  on  an  accompanying  page  of  the  notes,  using 
letters  to  refer  to  the  parts  indicated.  For  sample  legends  see 
Principles,  Figs.  3,  57,  58,  59,  169,  and  248.  Give  the  approxi- 
mate magnification  when  this  is  not  evident.  Explain  in  the 
notes  all  the  points  not  shown  in  the  sketches,  such  as  character- 
istic color,  consistency,  etc.  Think  out  everything  before  begin- 
ning to  write  a  description,  and,  if  it  is  lengthy,  draw  up  a  brief 
outline  so  that  your  notes  have  an  orderly  arrangement  like  the 
form  of  an  essay.  Write  the  notes  in  connection  with  the  mate- 
rial and  in  the  laboratory. 

6.  In  describing  an  experiment  record  in  separate  paragraphs 
what  you  did,  what  the  results  were,  and  your  conclusions  from 
them.  Do  not  leave  out  any  little  detail  that  may  have  influenced 
the  results  ;  for  instance,  if  in  a  germination  experiment  the  seeds 
were  allowed  to  get  too  dry.  Make  your  record  on  the  spot.  Do 
not  go  to  the  laboratory  to  observe  the  progress  of  an  experiment 
and  write  part  or  all  of  your  notes  elsewhere,  but  put  down  the 
results  in  the  presence  of  the  materials  and  apparatus  used. 

7.  If  not  original  with  yourself,  always  record  the  source  from 
which  any  statements  were  obtained,  thus :  "  Experiment  IX, 
Results  obtained  by  instructor  in  performing  the  experiment 
before  the  class." 

8.  Be  neat  and  accurate.  Forty  pages  of  well-written,  clearly 
expressed,  and  exact  notes  are  worth  more  than  a  hundred  pages 
of  disorderly  and  inaccurate  ones. 

The  Construction  and  Use  of  the  Compound 
Microscope 

A.  The  chief  parts  of  a  compound  microscope  are : 

1.  The  base  which  rests  on  the  table,  generally  horseshoe 
in  form. 


COXSTRUCTIOX    OF   THE    MICROSCOl'E  11 

2.  The  stage,  a  horizontal  shelf  ii]U)ii  which  is  placed  the 
preparation  or  slide  to  be  examined.  'Hie  stage  is  attached 
to  the  column. 

3.  The  mirror,  situated  below  the  stage,  by  which  the  light  is 
reflected  upward  through  the  opening  in  the  stage. 

4.  The  diaphragm  of  various  forms,  frequently  accompanied 
by  light  condensers,  attached  to  the  lower  side  of  the  stage 
and  used  to  regulate  the  intensity  of  the  light  reflected  by 
the  mirror. 

5.  The  tube,  a  cylinder  which  holds  the  lenses  and  moves 
up  and  down  perpendicularly  above  the  opening  in  the 
stage.  The  tube  is  raised  or  lowered  either  by  sliding  it 
back  and  forth  with  a  turning  movement  or  by  a  rack 
and  pinion  mechanism.,  This  mechanism  is  called  the 
coarse  adjustment. 

6.  The  fine  adjustment,  a  milled  head  back  of  the  tube, 
which,  on  being  turned,  moves  for  a  very  short  distance 
the  entire  framework  that  holds  the  tube. 

7.  The  lenses,  of  two  sorts,  —  eyepieces  or  oculars  which  slip 
into  the  upper  end  of  the  tube,  and  objectives  which  screw 
in  at  the  bottom.  An  important  accessory  to  the  tube  is 
the  7iose  piece,  capable  of  carrying  two  or  three  objectives 
which  may  be  revolved  into  place  at  the  lower  end  of  the 
tube.  A  student's  microscope  will  generally  be  fitted  witli 
two  eyepieces,  high  and  low,  and  with  two  objectives,  high 
and  low,  and  these  may  be  combined  with  one  another  to 
give  four  grades  of  magnification  ranging  generally  from 
about  50  to  more  than  500  diameters.  If  the  objectives  are 
respectively  §  inch  and  i  inch  and  the  eyepieces  2  inches 
and  1  inch,  the  lower  objective  with  either  eyepiece  will 
give  a  low  power,  the  higher  objective  with  the  2-inch  eye- 
piece a  medium  power,  and  the  higher  objective  and  1-inch 
eyepiece  a  high  poicer. 

8.  The  stand  consisting  of  the  microscope  Avithout  the 
lenses. 


>  LAliOllATORY   MinHODS  AND  EQUIPMENT 

B.  To  set  the  microscope  up  : 

1.  Lift  it  out  of  its  case  by  the  lower  part  of  the  column  to 
which  the  stage  is  attached,  never  by  the  tube  or  where  the 
fine  a^djustment  operates. 

2.  Place  it  on  the  table  with  the  fine  adjustment  nearest  you. 

3.  Screw  the  objectives  into  the  nose  piece  and  slip  an 
ocular  into  the  upper  end ;  turn  the  lowest  power  objec- 
tive into  position. 

4.  Find  the  light  by  looking  into  the  eyepiece  and  at  the 
same  time  turning  the  mirror  at  such  an  angle  that  it 
reflects  light  from  the  window  up  through  the  opening  in 
the  stage  to  the  objective.  When  a  clear,  bright  field  is 
obtained  the  microscope  is  set  up. 

5.  Kegulate  the  quantity  of  the  light  by  the  diaphragm.  If 
too  bright  it  must  be  cut  off  somewhat.  The  higher  powers 
require  brighter  light  than  the  lower.  Mirrors  generally 
have  two  faces,  a  plane  and  a  concave.  The  concave  mirror 
is  used  with  the  high-power  objectives. 

C.  To  find  the  object: 

1.  Place  the  slide  on  the  stage,  which  should  always  be 
horizontal,  with  the  object  over  the  middle  of  the  opening 
through  which  light  is  thrown  from  the  mirror. 

2.  With  the  lower  power  in  position  move  the  coarse  ad- 
justment until  either  the  object  or  small  solid  particles 
on  the  slide  appear  distinctly,  which  means  that  the  lenses 
are  in  focus.  The  object,  if  not  under  the  lens,  may  now  be 
brought  into  the  field  by  moving  the  slide  back  and  forth 
very  slowly.  The  focus  of  the  coarse  adjustment  may  gen- 
erally be  improved  upon  by  the  fine  adjustment. 

3.  To  focus  with  the  high-power  objective,  first  find  the 
object  with  the  low  power  and  arrange  in  the  center  of  the 
field.  Then  turn  the  high-power  objective  into  position.  In 
well-made  instruments  it  will  generally  be  found  to  come 
nearly  into  focus,  and  a  slight  movement  of  the  fine  adjust- 
ment will  show  the  object  clearly.    If  not  in  focus,  move 


USE  OF  THE  MICROSCOPE  13 

the  tube  slowly  downward  until  the  objective  nearly 
touches  the  slide,  watching  it  carefully  from  the  side,  and 
then  raise  it  by  the  fine  adjustment  until  the  focus  is  es- 
tablished. Never  focus  down  with  the  high-power  objec- 
tive because  of  the  danger  of  pressing  it  into  the  slide  and 
ruining  the  delicately  mounted  lenses. 
D.  Studying  an  object : 

1.  Always  examine  an  object  first  with  the  low  powers  so 
as  to  understand  its  general  structure  before  passing  to 
details. 

2.  Obtain  greater  magnification,  if  the  instrument  permits, 
by  using  more  powerful  objectives  rather  than  higher  eye- 
pieces, for  owing  to  peculiarities  of  the  lenses  clearer 
images  are  thus  obtained. 

3.  Do  not  rest  satisfied  until  the  light  is  of  the  best  quality 
obtainable  with  the  mirror  and  diaphragm.  It  should  not  be 
too  bright.  Details  are  shown  more  clearly  by  subdued  light. 

4.  Keep  both  eyes  open  in  using  a  microscope.  If  this  is 
at  first  distracting,  cover  the  free  eye  with  the  fingers 
or  by  a  paper  screen  projecting  from  the  microscope  tube 
until  it  is  no  longer  attracted  by  surrounding  objects 
on  the  table  and  the  attention  is  entirely  concentrated 
on  the  working  eye.  Never  let  the  habit  of  squinting 
develop. 

5.  If  it  is  necessary  to  ascertain  the  exact  size  of  an  object 
this  can  best  be  done  by  the  use  of  two  micrometers.  The 
eyepiece  micrometer  consists  of  a  disk  of  glass  ruled  with 
fine  equidistant  lines ;  this  is  inserted  beneath  the  upper 
lens  of  the  eyepiece.  The  stage  micrometer  is  a  glass  slide 
ruled  with  fine  lines  1-100  mm.  apart.  To  measure  an 
object  the  number  of  spaces  on  the  eyepiece  micrometer 
which  its  image  covers  must  be  noted.  Then  the  value  of 
each  space  is  to  be  ascertained  by  substituting  for  the 
object  the  stage  micrometer.  A  simple  calculation  will 
now  give  the  diameter  of  the  object. 


14  LAHOKATOUV   .MKTIKJDS  AND   KQUIPME^'T 

E.  Rules  for  the  use  of  the  microscope : 

1.  Never  allow  the  objective  to  touch  the  cover  glass  or  the 
liquid  iu  which  the  object  is  niouuted. 

2.  Do  not  handle  the  front  lens  of  the  objective  or  unscrew 
the  sections  in  which  the  lenses  are  mounted. 

o.  (Uean  the  front  lens  of  the  objective  only  when  neces- 
sary, and  then  with  small  pieces  of  lens  paper,  which  should 
be  thrown  away  after  use,  or  with  an  old  clean,  soft  hand- 
kerchief. Breathe  on  the  lens  before  cleaning  it,  or,  if  that 
is  not  sufficient,  moisten  the  lens  paper  with  a  drop  of 
xylol,  taking  care  to  wipe  it  perfectly  dry  as  quickly  as 
possible. 

4.  Do  not  let  the  objective  remain  long  near  volatile  corro- 
sive liquids  such  as  hydrochloric  or  nitric  acid  or  strong 
solutions  of  iodine. 

5.  Do  not  allow  liquids  to  run  from  the  slide  over  the  stage 
or  other  parts  of  the  microscope. 

6.  Keep  the  microscope  covered  with  a  bell  jar  or  paper 
cone  when  not  in  use,  and  keep  the  objectives  and  eye- 
pieces away  from  dust. 


Part  I 

STRUCTURE  AND  PHYSIOLOGY  OF 
SEED  PLANTS 


INTKODUCTORY  STUDY  OF  A  SEED  PLANT 
AND  ITS  OKGANS 

1.  The  common  dwarf  nasturtium  (Tropaeolum).^ 

A.  The  plant  body.  Take  a  plant  which  has  been  carefully  dug 
up  and  note  the  division  of  the  plant  body  into  three  sets 
of  parts  or  organs,  roots,  stems,  and  leaves,  which  constitute 
its  main  bulk. 

Make  a  reduced  drawing  to  show  the  general  form  and 
proportions  of'  the  entire  plant. 

B.  Roots.  Note  the  general  form  and  arrangement  of  the  roots 
and  the  differences  between  roots  and  stem  in  size,  shape, 
color,  and  texture. 

C.  Stem.  Make  a  reduced  drawing  of  a  portion  of  the  stem, 
with  parts  of  two  or  three  leafstalks,  showing  how  they  are 
attached  to  it.   Does  the  stem  branch  ?   Is  it  solid  or  hollow  ? 

D.  Leaves.  Make  a  reduced  drawing  of  one  of  the  largest 
leaves,  including  the  leafstalk,  and  life-size  drawings  of  two 
or  three  of  the  youngest  leaves  near  the  tip  of  the  stem. 
Note  the  mode  of  attachment  of  the  leafstalk  to  the  expanded 
portion,  blade,  of  the  leaf,  the  course  of  the  veins  through 
the  blade,  and  the  differences  between  the  upper  and  lower 
surfaces  of  the  latter. 

1  Auy  plant  witli  well-developed  roots,  stems,  aud  leaves,  and  simple,  conspicu- 
ous tloweis,  will  answer  for  this  study.  Good  types  available  in  autumn  are  the 
garden  balsam,  the  wild  yellow  oxalis  (O.  corniculata),  the  petunia,  auy  of  the 
Gerardias,  etc. 

16 


16     STRUCTURE   AND  PHYSIOLOGY  OF   SEED  PLANTS 

Roots,  stems,  and  leaves  taken  together  constitute  the  vegeta- 
tive organs  of  the  plant  body,  or  the  apparatus  by  which  it 
carrit^s  on  the  processes  necessary  for  its  life  and  growth. 
In  a  general  way  it  may  be  said  that  the  roots  serve  to  anchor 
tlie  plant  and  to  absorb  water  and  dissolved  raw  materials 
from  the  soil  to  aid  in  the  manufacture  of  plant  food,  that 
the  stem  conducts  water  and  plant  foods,  and  that  the  leaves 
carry  on  most  of  the  work  of  food  making  for  the  plant  and 
of  admitting  oxygen  for  respiration. 
E.   Thejiower.  Note  the  occurrence  of  flowers  at  intervals  along 
the  stem.    Locate  the  points  from  which  flowers  may  arise. 
Sketch  a  short  section  of  the  stem  with^a  flower  attached. 
Make  a  drawing  of  a  flower  (side  view),  noting  the  sjmr  which 
extends  for  some  distance  nearly  parallel  to  the  flower  stalk. 
Examine  the  outer  surface   and  the  inner   surface   of  the 
flower  to  see  how  the  somewhat  leaf -like  but  bright-colored 
parts  which  inclose  it  are  related  to  each  other.     The  five 
outer  portions  together  make  up  the  calyx,  and  the  five 
inner  ones  the  corolla.    Calyx  and  corolla  together  consti- 
tute the  perianth.    Cut   away  the  members  of  the  corolla 
and  note  in  the  interior  of  the  flower  the  eight  curved  stalks, 
each   surmounted   by  a  knob,   and  within  them  a  smaller 
object,  split  at  the  tip   into  three  divisions.    The  knobbed 
organs  are  stame7is  and  the  innermost  organ  is  a  pistil. 
Y.   The  fruit.    Find  a  series  of  old  flowers  in  which  the  cal3'x 
and  corolla  have  become  more  and  more  withered,  and  trace 
the  development  of  the  lower  part  of  the  pistil  into  a  green 
three-lobed//va^.    Cut  across  a  large,  nearly  dry  fruit  and  find 
out  how  many  seeds  are  contained  in  each  of  its  divisions. 
2.  Reproduction  in  the  seed  plant.    Stamens  and  pistils  taken 
together  constitute  the   rei^roductive  organs  of  the  plant.    The 
calyx  and  corolla  aid  the  work  of   the  stamens  and  pistils  in 
various  mechanical  and  other  ways.^    The  use  of  the  flower  is  to 
bear  seed,  and  seed  formation  is   brought  about  by  the  action 
1  See  Principles,  Chapter  XXXIL 


THE   SEED  AND  ITS   GERMINATION  17 

of  the  pollen  (a  substance  produced  by  the  stamens)  ^  on  the 
rudimentary  seeds,  known  as  ondes,  borne  within  the  divisions  of 
the  three-lobed  base  of  the  pistil. 

3.  Life  history.  The  life  h  Isfort/  of  every  seed  plant  comprises 
the  series  of  changes  which  it  undergoes  in  springing  from  a  seed, 
growing  to  maturity,  and  producing  flowers  and  seed  of  its  own. 

THE   SEED  AND  ITS   GEKMINATION 

4.  Germination  of  the  squash  seed.*  *  Soak  some  squash  seeds  in 
tepid  water  for  twelve  hours  or  more.  Plant  these  about  an  inch 
deep  in  damp  sand,  pine  sawdust,  or  peat  moss,  in  a  wooden  box 
which  has  had  holes  enough  bored  through  the  bottom  to  prevent 
its  holding  water.  l*ut  the  box  in  a  warm  place  (not  at  any 
time  over  70°-80°  Fahrenheit,  or  21°-27°  Centigrade),  and  cover 
it  loosely  with  a  board  or  a  pane  of  glass.  Keep  the  sand  or 
sawdust  moist,  but  not  wet,  and  the  seeds  will  germinate.  As 
soon  as  any  of  the  seeds,  on  being  dug  up,  are  found  to  have 
burst  open,  sketch  one  in  this  condition,  noting  the  manner  in 
which  the  outer  seed  coat  is  split.  Look  for  the  ^^e^,  a  kind  of 
knob,  or  hook,  at  the  base  of  the  hypocotyl,  and  see  what  it  has 
to  do  with  the  actions  of  the  seedling.  Continue  to  examine  the 
seedling  at  intervals  of  two  days,  until  at  least  eight  stages  in 
the  growth  of  the  plantlet  have  been  noted. 

Observe  particularly  how  the  sand  is  pushed  aside  by  the  rise 
of  the  young  seedlings.  Suggest  some  reason  for  the  manner  in 
which  the  sand  is  penetrated  by  the  rising  stem. 

5.  Examination  of  the  squash  seed.*  *  Make  a  sketch  of  the  dry 
seed,  natural  size. 

A.  Note  the  scar  at  the  pointed  end  of  the  seed  where  the 
latter  was  attached  to  its  place  of  growth  in  the  squash. 
Label  this  hilum. 

B.  Note  the  little  hole  near  the  hilum  ;  it  is  the  micropyle,  seen 
most  plainly  in  a  soaked  seed. 

^  In  the  nasturtium  the  pollen  is  a  yellow,  rather  sticky  powder. 


18     STliUCTURJb:  AND  PlIYSIOLOCiY   OF   SEED  PLANTS 

C.  Describe  the  color  and  texture  of  the  outer  coating  of 
the  seed.  With  a  scalpel  or  a  very  sharp  knife  cut  across 
near  the  middle  a  seed  that  has  been  soaked  in  water  for 
twenty-four  hours.  Examine  with  the  dissecting  microscope 
and  sketch  the  section  thus  treated. 

D.  Taking  another  soaked  seed,  chip  away  the  white  outer 
shell,  called  the  testa,  and  observe  the  thin,  greenish,  inner 
skin  with  which  the  kernel  of  the  seed  is  closely  covered. 

E.  Strip  this  off  and  sketch  the  uncovered  kernel  or  embryo. 
Note  that  at  one  end  it  tapers  to  a  point.  This  pointed 
portion,  known  as  the  hyioocotijl,  after  the  seed  sprouts  will 
develop  into  the  stem  of  the  plantlet.  Split  the  "  halves  "  of 
the  kernel,  seed  leaves  or  cotyledons,  entirely  apart  from  each 
other,  and  note  where  and  to  what  extent  they  are  connected. 

F.  Have  ready  some  seeds  which  have  been  soaked  for  twenty- 
four  hours  and  then  left  in  a  loosely  covered  jar  on  damp 
blotting  paper  at  a  temperature  of  70°  Fahrenheit  (21°  Centi- 
grade) or  over  until  they  have  begun  to  sprout.  Split  one  of 
these  seeds  apart,  separating  the  cotyledons,  and  observe,  at 
the  junction  of  these,  two  very  slender  pointed  objects,  the 
rudimentary  leaves  of  the  plmnule  or  first  bud. 

6.  Examination  of  the  bean.  Study  the  seed,  both  dry  and 
after  twelve  hours'  soaking,  in  the  same  way  in  which  the  squash 
seed  has  just  been  examined. 

A.  Notice  the  presence  of  a  distinct  plumule,  consisting  of  a 
pair  of  rudimentary  leaves  with  a  minute  stem,  between  the 
cotyledons,  just  where  they  are  joined  to  the  top  of  the 
hypocotyl.  In  many  seeds  (as  the  pea)  the  plumule  does 
not  show  the  distinct  leaves,  but  in  all  cases  it  contains  the 
growing  point,  the  tip  of  the  stem  from  which  all  the  upward 
growth  of  the  plant  is  to  proceed. 

B.  Make  a  sketch  of  these  leaves  as  they  lie  in  place  on  one  of 
the  cotyledons,  after  the  bean  has  been  split  open. 

Note  the  cavity  in  each  cotyledon  caused  by  the  pressure  of 
the  plumule  and  of  the  hypocotyl. 


KELAllON    OF   TEMrERATUKE   TO   GERiMlNA'J  ION     19 

7.  Examination  of  the  pea.  There  are  no  very  important  points 
of  difference  between  the  bean  and  pea,  so  far  as  the  structure 
of  the  seed  is  concerned,  but  the  student  should  rapidly  dissect 
a  few  soaked  peas  to  gain  an  idea  of  the  appearance  of  the  parts, 
since  he  is  to  study  the  germination  of  the  pea  in  detail. 

Make  only  one  sketch,  that  of  the  hypocotyl  as  seen  in  posi- 
tion after  the  removal  of  the  seed  coats. 

8.  Germination  of  the  bean  (or  the  white  lupine),  the  pea,  and  the 
grain  of  corn.*  *  Soak  some  beans  or  lupine  seeds  as  directed  in 
Sec.  4,  plant  them,  and  make  a  series  of  sketches  on  the  same 
general  plan  as  those  in  Principles,  Fig.  8. 

Follow  the  same  directions  with  some  peas  and  some  corn.  In 
the  case  of  the  corn,  .make  six  or  more  sketches  at  various  stages 
to  illustrate  the  growth  of  the  plumule  and  the  formation  of  roots. 
The  student  may  be  able  to  discover  what  becomes  of  the  large 
outer  part  of  the  embryo.  This  is  believed  to  be  the  single  coty- 
ledon of  the  corn.  It  does  not  as  a  whole  rise  above  ground,  but 
most  of  it  remains  in  the  buried  grain,  and  acts  as  a  digest- 
ing and  absorbing  organ  through  which  the  endosperm,  or  food 
stored  outside  of  the  embryo,  is  transferred  into  the  growing 
plant  as  fast  as  it  can  be  made  liquid  for  that  purpose. 

9.  Germination  of  the  horse-chestnut.  Plant  some  seeds  of  the  horse- 
chestnut  or  the  buckeye,  study  their  mode  of  germination,  and  observe  the 
nature  and  pecuUar  modification  of  the  parts. 

EXPERIMENT  I* 

Relation  of  temperature  to  germination.*  *  Prepare  at  least  four 
beakers  or  tumblers,  each  with  wet,  soft  paper  packed  in  the 
bottom  to  a  depth  of  nearly  an  inch.  Have  a  tightly  fitting 
cover,  such  as  a  square  of  window  glass  or  a  '^  clock  glass,"  over 

*  To  THE  Instkuctok:  As  some  of  the  experiuieuts  upon  seeds  occupy  a  good 
uiauy  days  or  weeks  for  their  completion,  the  laboratory  work  should  be  pushed 
on  without  waiting  until  these  are  finished.  Results  may  be  discussed  from  time 
to  time  while  the  experiments  are  in  progress  and  summed  up  when  they  are  en- 
tirely finished. 


20     STRUCTURE  AND  PHYSIOLOGY  OF  SEED  PLANTS 

each.  Put  in  each  vessel  the  same  number  of  soaked  peas  of  about 
the  same  size.  Stand  the  vessels  with  theii-  contents  in  places 
where  they  will  be  exposed  to  different,  but  fairly  constant,  tem- 
peratures, and  the  same  conditions  as  regards  light,  and  observe 
the  several  temperatures  carefully  with  a  thermometer.  Take 
pains  to  keep  the  tumblers  in  the  warm  places  from  drying  out, 
so  that  their  contents  will  not  be  less  moist  than  those  of  the 
others.  The  following  series  is  merely  suggested;  other  values 
may  be  found  more  convenient.  Note  the  rate  of  germination  in 
each  place  and  record  in  tabular  form  as  follows : 

No.  of  seeds  sprouted  in  l4  hr.        48  hr.  72  hr.  %  hr.        etc. 

At  32°  F.  (0°  C.) 

At  50°  F.  (10°  C.)   

At  70°  F.  (21°  C.)  

At  90°  F.  (32°  C.)  

If  a  thermostat  can  be  had,  it  should  be  used  to  control  the 
temperatures,  and  the  highest  point  at  which  germination  can 
take  place  should  be  noted. 

EXPERIMENT  II 

Amount  of  water  in  air-dry  seeds  and  amount  absorbed  to  produce  germination. 

A.  Weigh  accurately  a  convenient  quantity  of  seeds,  and  then  dry  them 
on  the  water  bath  until  they  no  longer  lose  weight.!  Report  the  loss  of 
weight  as  water  and  calculate  what  per  cent  it  constituted  of  the  total 
weight. 

B.  Weigh  a  new  set  of  seeds  from  the  original  (undried)  lot,  place  them 
between  layers  of  porous  white  paper  kept  thoroughly  moist  but  not 
dripping  wet,  cover  them,  and  allow  them  to  remain  until  the  germina- 
tion is  evidently  begun.  Reweigh  the  seeds,  and  calculate  the  increase 
of  weight  by  absorption  of  water  and  the  per  cent  of  absorbed  water. 2 

This  last  will  be 

weight  water  absorbed 

weight  air-dry  seeds 

^  This  may  be  done  once  for  all  for  the  entire  laboratory  division. 
2  The  gain  in  weight  observed  may  be  a  trifle  less  than  the  total  value,  since 
some  loss  of  weight  by  oxidation  is  certain  to  have  occurred. 


STORACiE   OF    FOOD    IN     TlIK   SEEJ)  '21 

EXPERIMENT  IIT 

Will  seeds  germinate  well  without  a  good  supply  of  air  ?  *  * 

A.  Place  some  soaked  seeds  on  damp  blotting  paper  in  the 
bottom  of  a  bottle,  using  seeds  enough  to  fill  it  three  quar- 
ters full,  and  close  tightly  with  a  rubber  stopper. 

B.  Put  a  few  other  seeds  of  the  same  kind  in  a  second  bottle, 
and  cover  loosely.  Place  the  bottles  side  by  side,  so  that  they 
will  have  the  same  conditions  of  light  and  heat.  Watch  for 
results  and  tabulate  as  in  previous  experiments. 

EXPERIMENT  IV 

Effect  of  germinating  seeds  upon  the  surrounding  air.*  *  When 
Exp.  Ill  has  been  finished  remove  a  little  of  the  air  from  above 
the  peas  in  the  first  bottle.  This  can  easily  be  done  with  a  rubber 
bulb  attached  to  a  short  glass  tube.  Then  bubble  this  air  through 
some  clear  limewater  made  by  slaking  quicklime  in  warm  water 
and  filtering  through  a  paper  filter.  Also  blow  the  breath  through 
some  limewater  by  aid  of  a  short  glass  tube.  Explain  any  similar- 
ity in  results  obtained.  (Carbon  dioxide  turns  limewater  milky.) 
Afterwards  insert  into  the  air  above  the  peas  in  the  same  bottle 
a  lighted  pine  splinter,  and  note  the  effect  upon  its  flame. 

STOEAGE  OF  FOOD  IN  THE   SEED 
EXPERIMENT  V 

Are  the  cotyledons  of  a  pea  of  any  use  to  the  seedling?  Sprout 
several  peas  on  blotting  paper.  When  the  plumules  appear 
carefully  cut  away  the  cotyledons  from  some  of  the  seeds.  Place 
on  a  wide,  perforated  cork  one  or  two  seedlings  from  which  the 
cotyledons  have  been  cut,  and  as  many  which  have  not  been 
mutilated.  Put  the  cork  in  the  mouth  of  a  cylindrical  glass  jar 
of  water,  which  it  should  fit  moderately  well,  and  allow  the  roots 
to  extend  into  the  water,  which  must  be  kept  always  at  the  same 
level.    Let  them  grow  for  some  weeks  and  note  results. 


22     STKUCTriiE   AND   PIIYSIOLOCiY   OF   SEED  TLANTS 

EXPERIMENT  VI 

Does  the  amount  of  material  in  the  seed  have  anything  to  do  with  the  rate 
of  growth  of  the  seedling  ?  Germinate  ten  or  more  clover  seeds,  and  about 
the  same  number  of  peas,  on  moist  blotting  paper  under  a  bell  jar.  After 
they  are  well  sprouted  transfer  both  kinds  of  seeds  to  tine  cotton  netting, 
stretched  across  wide-mouthed  jars  nearly  full  of  water.  Only  the  roots  of 
the  seedlings  should  touch  the  water.  Allow  the  plants  to  grow  until  the 
peas  are  from  four  to  six  inches  high. 

10.  Examination  of  the  four-o'clock  seed.i  Examine  the  external  surface 
of  a  seed  of  the  four-o'clock,^  and  note  the  hardness  of  the  outer  coat.  From 
seeds  which  have  been  soaked  in  water  at  least  twenty-four  hours  peel  off 
the  coatings  and  sketch  the  kernel.  Make  a  cross  section  of  one  of  the 
entire  soaked  seeds  and  sketch  the  section  as  seen  with  the  magnifying 
glass,  to  show  the  parts,  especially  the  two  cotyledons,  lying  in  close  contact 
and  encircling  the  white,  starchy-looking  endosperm.  With  a  mounted  needle 
pick  out  the  little  almost  spherical  mass  of  endosperm  from  inside  the  coty- 
ledons of  a  seed  which  has  been  deprived  of  its  coats,  and  sketch  the  embryo, 
noting  how  it  is  curved  so  as  to  inclose  the  endosperm  almost  completely. 

11.  Examination  of  the  kernel  of  Indian  corn.*  *  Soak  some  grains 
of  large  yellow  field  corn  for  about  two  days. 

A.  Sketch  an  unsoaked  kernel  so  as  to  show  the  grooved  side, 
where  the  germ  lies.  Observe  how  this  groove  has  become 
partially  filled  up  in  the  soaked  kernels. 

B.  Remove  the  thin,  tough  skin  from  one  of  the  latter  and 
notice  its  transparency.  This  skin  —  the  bran  of  unsifted 
corn  meal  —  does  not  exactly  correspond  to  the  testa  and 
inner  coat  of  ordinary  seeds,  since  the  kernel  of  corn,  like 
all  other  grains  (and  like  the  seed  of  the  four-o'clock),  repre- 
sents not  merely  the  seed  but  also  the  seed  vessel  in  which 
it  was  formed  and  grew,  and  is  therefore  a  fruit. 

C.  Cut  sections  of  the  soaked  kernels,  some  transverse,  some 
lengthwise  and  parallel  to  the  fiat  surfaces,  some  lengthwise 
and  at  right  angles  to  the  flat  surfaces.  Try  the  effect  of 
staining  some  of  these  sections  with  iodine  solution.  Make 
a  sketch  of  one  section  of  each  of  the  three  kinds,  and  label 

1  Strictly  speaking  a  fruit. 

2  Morning-glory  seeds  or  grains  of  buckwheat  also  answer  well. 


RECOGNITION   OF   SUBSTANCES  IN    PLANTS  23 

the  dirty  white  portion,  of  cheesy  consistency,  emhri/n ;  and 
the  yellow  portions,  and  those  which  are  white  and  floury, 
endospevDi. 
D.  Chip  off  the  endosperm  from  one  kernel  so  as  to  remove 
the  embryo  free  from  other  parts.  Notice  its  form,  some- 
what triangular  in  outline,  sometimes  nearly  the  shape  of 
a  beechnut,  and  in  other  specimens  nearly  like  an  almond. 
Estimate  what  proportion  of  the  entire  bulk  of  the  soaked 
kernel  is  embryo  (^Principles,  Fig.  378).  Split  the  embryo 
lengthwise  so  as  to  show  the  slender  plumule. 

12.  Recognition  of  some  chemical  compounds  found  in  plants.*  *  Out  of  the 
very  numerous  substances  which  make  up  the  framework  of  the  plant  body, 
or  are  stored  in  it,  there  are  several  most  important  ones  which  the  student 
should  be  able  to  recognize  by  simple  tests.  In  this  place  only  starch,  sugar, 
cellulose,  lignin,  oil,  and  proteids  will  be  discussed. 

A.  Starch.  This  turns  blue,  or  nearly  black,  on  the  addition  of  iodine 
solution.  Make  the  test  on  a  bit  of  laundry  starch  the  size  of  a  grain 
of  wheat  diffused  in  a  large  test  tube  full  of  boiling  water  ;  it  does  not 
form  a  true  solution.  Add  the  iodine  solution  (Sec.  1G9)  drop  by  drop 
to.  the  boiled  starch  after  the  latter  has  cooled. 

B.  Sugar.  Some  of  the  sugars  found  in  plants  produce  a  yellow  or  orange 
color  or  an  orange  precipitate  on  being  heated  to  boiling  with  a  solution 
of  copper  known  as  Fehling's  solution  (Sec.  170).  Cane  sugar  does  not 
give  the  reaction  readily  unless  it  has  first  been  boiled  with  dilute 
hydrochloric  acid,  when  it  responds  promptly  to  the  test.  Make  the 
test  with  Fehling's  solution  on  a  rather  dilute  solution  of  commercial 
glucose  in  hot  water. 

C.  Cellulose.  This  turns  blue  on  being  moistened  with  iodine  solution 
and  then  witli  concentrated  sulphuric  acid  diluted  with  half  its  bulk 
of  water.  Make  the  test  with  a  bit  of  absorbent  cotton  (in  this  par- 
ticular case  wetting  the  cotton  first  with  the  acid  and  then  with  the 
iodine  solution). 

D.  Lignin.  This  substance,  which  forms  a  large  part  of  the  material  of 
lignified  cell  walls,  gives  a  reddish  violet  color  with  phloroglucin  solution 
(Sec.  170)  after  the  addition  of  hydrochloric  acid.  Make  the  test  by 
moistening  a  thin  shaving  of  any  kind  of  light-colored  wood  with  a 
solution  of  as  much  phloroglucin  as  can  be  taken  up  on  the  point  of  a 
penkfUife  in  thirty  or  forty  drops  of  95  per  cent  alcohol.  Then  wet  the 
moistened  shaving  with  a  little  concentrated  hydrochloric  acid. 


24     STRrc'rillE   AM)    I'llVSIOLOGY   OF   SEED   PLANTS 

E.  Oil.  Oils  may  be  recognized  by  their  characteristic  appearance  as  seen 
in  minute  droplets  in  the  tissues  of  the  plant  when  examined  with  the 
microscope.  Thin  sections  containing  oil,  when  treated  with  ether  or 
chloroform,  lose  the  oil  almost  instantly.  Oils  (and  resins  also)  are 
colored  a  deep  red  by  the  alcoholic  solution  of  alkannin  (Sec.  170)  or  of 
the  soluble  material  in  alkanet  root.  Make  the  test  on  a  thin  section  of 
an  oily  seed  (not  Ricinus  seed)  placed  under  the  microscope  in  an 
alcoholic  solution  of  alkannin. 

F.  Proteids.  Proteids  usually  give  a  brick-red  or  rose-red  color  when 
moistened  with  Millon's  reagent  (Sec.  170)  and  gently  heated.  They 
are  stained  yellow  or  brown  by  iodine  solution.  All  proteids  turn 
yellow  {xanthoproteic  reaction)  when  moistened  with  strong  nitric  acid 
and  slightly  warmed.  The  color  deepens  on  the  addition  of  ammonia 
water  to  the  stained  substance.  To  make  the  nitric-acid  test,  warm  a 
little  egg  albumen  with  the  strong  acid,  and  when  the  coagulated 
albumen  becomes  decidedly  yellow  pour  off  the  excess  of  acid  and 
cover  the  stained  mass  with  a  little  ammonia  water. 

References.  For  the  substances  to  be  tested,  Principles;  Pfeffer,  31  ;  for 
the  tests  themselves,  Zimmerman's  Botanical  Microtechnique  (Henry 
Holt  &  Co.,  New  York),  and  Strasburger-Hillhouse,  6. 


EXPERIMENT  VII 

Occurrence  of  starch  in  seeds.  Cut  in  two  with  a  sharp  knife  the 
seeds  to  be  experimented  on,  and  then  pour  on  each,  drop  by 
drop,  some  iodine  solution.  Only  a  little  is  necessary  ;  sometimes 
the  first  drop  is  enough. 

If  starch  is  present  a  blue  color  (sometimes  almost  black)  will 
appear.  If  no  color  is  obtained  in  this  way,  boil  the  pulverized 
seeds  for  a  moment  in  a  few  drops  of  water  and  try  again. 

Test  in  this  manner  corn,  wheat  (in  the  shape  of  flour),  oats 
(in  oatmeal),  barley,  rice,  buckwheat,  flax,  rye,  sunflower,  four- 
o'clock,  morning-glory,  mustard  seed  (not  ground  mustard),  beans, 
peanuts,  Brazil  nuts,  hazelnuts,  and  any  other  seeds  that  you  can 
get.    Report  results  in  tabular  form. 

Reference.    Strasburger-Hillhouse,  6. 

13.  Absorption  of  starch  from  the  cotyledons.  Examine  with  the  micro- 
scope, using  m.p.  (medium  power),  thin  sections  of  soaked  beans  and  the 


STRUCTURE   OF   STAlfCTI  25 

cotyledons  from  seedlings  that  have  been  growing  for  three  or  four  weeks. 
Stain  the  sections  with  iodine  solution,  and  notice  how  completely  the  clusters 
of  starch  grains  that  filled  most  of  the  cells  of  the  unsprouted  cotyledons  have 
disappeared  from  the  shriveled  cotyledons  of  the  seedlings. 

References.    Strasburger-Hillhquse,  6;  Tschirch,  74. 

14.  Structure  of  starch.*  * 

A.  Cut  moderately  thin  sections  of  a  potato  tuber,  mount  in 
water,  and  examine  with  m.p.  (medium  power).  Note  the 
starch  grains  inclosed  in  little  chambers  or  cells.  Kun  in  a 
little  weak  iodine  solution  (Sec.  169)  under  one  edge  of  the 
cover  glass,  at  the  same  time  withdrawing  water  from  the 
opposite  edge  with  a  bit  of  blotting  paper.  Watch  the  sec- 
tion carefully  during  the  process  and  note  the  gradual  stain- 
ing of  the  starch  grains.     Draw. 

B.  Mount  in  water  some  pulp  scraped  from  a  freshly  cut  sur- 
face of  potato  and  examine  with  h.p.  (high  power).  Move  the 
fine  adjustment  constantly  while  observing,  and  note  the  lines 
arranged,  somewhat  concentrically  about  a  point  called  the 
hilum,  often  marked  by  minute  cracks  in  the  grain.  Draw 
several  grains. 

Is  there  any  evidence  that  the  starch  grain  is  composed  of  suc- 
cessive layers  ?     If  so,  how  may  they  have  been  caused  ? 

C.  Draw  to  the  same  scale  as  seen  under  h.p.  all  the  principal  forms  and 
sizes  of  potato  starch  grains  that  you  can  find,  together  with  grains  of 
several  other  kinds,  as  canna  starch  (from  the  rootstock),  oat  starch, 
corn  starch,  and  Euphorbia  starch  (from  E.  splendens). 

References.    Strasburger-Hillhouse,  6 ;  Tschirch,  74. 


EXPERIMENT  VIII 

Determination  of  oil  in  flaxseed.  Weigh  out  two  ounces  (or  sixty 
grams)  of  ground  flaxseed  and  add  an  equal  volume  of  ether  or 
benzine.  Do  not  bring  tJiese  liquids  near  a  gas  Jet  or  an//  other 
flame.  Let  it  stand  ten  or  hfteen  minutes  and  then  filter.  Wash 
the  meal  by  pouring  over  it,  a  little  at  a  time,  about  the  same 


26     STRUCTURE  AND  PHYSIOLOGY  OF  SEED  PLANTS 

amount  of  liquid  as  was  used  at  first.  Let  the  liquid  stand  in  a 
saucer  or  evaporating  dish  in  a  good  draft  till  it  has  lost  the 
odor  of  the  ether  or  benzine.  Weigh  the  remaining  oil  and  cal- 
culate what  per  cent  of  the  ground  seed  was  oil.  (Traces  will  of 
course  still  be  left  in  the  residue  on  the  filter.) 

Describe  the  oil  which  you  have  obtained.  Of  what  use  would 
it  have  been  to  the  plant  ? 

EXPERIMENT  IX 

Detection  of  proteids  in  seeds.  Extract  the  germs  from  some 
soaked  kernels  of  corn  and  bruise  them,  or  soak  some  wheat-germ 
meal  for  a  few  hours  in  warm  water,  or  in  a  stream  of  water  wash 
the  starch  out  of  wheat-flour  dough ;  reserving  the  residue  for 
use,  place  it  in  a  white  saucer  or  porcelain  evaporating  dish  and 
moisten  well  and  heat  with  Millon's  reagent  (Sec.  170)  or  with 
nitric  acid ;  examine  after  fifteen  minutes.  Proteids  turn  yellow 
when  moistened  with  nitric  acid  and  red  with  Millon's  reagent. 

Referexce.    Strasburger-Hillhouse,  6. 


EXPERIMENT  X 

What  plant  foods  are  found  in  Brazil  nuts?  Crack  several  Brazil  nuts,  peel  off 
the  brown  coating  from  the  kernel  of  each,  and  then  grind  the  kernels  to  a 
pulp  in  a  mortar.  Shake  up  this  pulp  with  ether,  pour  upon  a  filter  paper,  and 
wash  with  ether  until  the  washings  when  evaporated  are  nearly  free  from 
oil.  The  funnel  containing  the  filter  should  be  kept  covered  as  much  as 
possible  until  the  washing  is  finished.  Evaporate  the  filtrate  to  procure  the 
oil.  Dry  the  powder  which  remains  on  the  filter  and  keep  it  in  a  wide-mouthed 
bottle.  Test  some  of  it  for  starch  and  for  proteids.  Does  it  appear  that  a 
seed  needs  to  contain  both  starch  and  oil,  or  may  one  replace  the  other  ? 

15.  Microscopical  study  of  reserve  oil  in  a  seed.  Cut  moderately  thin 
sections  of  an  oily  seed,  e.g.  peanut  (not  roasted).  Mount  in  water  and 
examine  with  m.p.  Note  the  cellular  structure  of  the  seed  and  the  minute 
oil  globules  within  the  cells.  Try  to  estimate  the  number  in  a  cell.  Mount 
another  section  in  an  alcoholic  solution  of  alkannin  or  of  the  soluble  portion 
of  alkanet  root  (Sec.  170).    After  a  few  minutes  examine  the  section  and  note 


STRUCTURE  OF  PROTEID  GRAINS         27 

the  stained  oil  globules.    Some  larger  droplets  of  oil  may  appear  outside  of 
the  section.    Sketch,  using  h.p.  if  necessary. 

References.     Strasburger-Hillhouse,  6  ;  Tschirch,  74. 

16.  Structure  of  proteid  grains  (aleurone  grains).  A  large  part  of  the  proteid 
reserve  material  of  seeds  is  stored  in  the  form  of  minute  bodies  known  as 
aleurone  grains.  They  occur  in  abundance  packed  around  the  starch  grains 
in  such  seeds  as  those  of  the  bean  and  pea,  but  are  more  easily  studied  in 
seeds  nearly  or  quite  free  from  starch.  Remove  the  testa  from  a  seed  of 
the  castor-oil  plant  {Ricinus)  and  cut  thin  sections  from  the  endosperm. 
Mount  in  olive  oil  (which  does  not  dissolve  any  of  the  proteid  material)  and 
examine  with  h.p.  Note  the  very  small  aleurone  grains,  each  with  a  clear  body 
at  the  narrow  end.  This  clear  body,  called  the  globoid,  is  of  mineral  material, 
principally  a  double  phosphate  of  lime  and  magnesia.  Draw  the  aleurone 
grains.  Mount  another  section  in  water  and  examine  ;  then  run  in  absolute 
alcohol  under  one  edge  of  the  cover  glass,  and  note  the  proteid  crystal,  which 
should  appear  plainly,  constituting  a  large  part  of  the  bulk  of  the  aleurone 
grain,  and  the  globoid.  The  latter  is  now  distinctly  recognizable  as  a  solid 
substance.    Draw. 

Aleurone  grains  may  be  more  easily  demonstrated  in  thin  sections  of  the 
kernel  of  the  Brazil  nut.  These  should  be  rinsed  twice  in  chloroform,  to 
remove  the  oil,  then  once  in  alcohol,  and  mounted  in  alcohol.  Examine 
with  h.p.,  run  in  iodine  solution  while  under  the  microscope,  and  note  the 
brown-stained  grains  in  the  cells.    Draw. 

References.    Strasburger-Hillhouse,  6;  Tschirch,  74. 


MOVEMENTS,  DEVELOPMENT,   AND  MORPHOLOGY 

OF   THE   SEEDLING 

EXPERIMENT  XI 

Is  the  arch  of  the  hypocotyl  due  to  the  pressure  of  the  soil  on  the  rising 
cotyledons  ?  Sprout  some  squash  seeds  on  wet  paper  under  a  bell  glass,  and 
when  the  root  is  an  inch  or  more  long  hang  several  of  the  seedlings,  roots 
down,  in  little  stirrups  made  of  soft  twine,  attached  by  a  mixture  of  equal 
parts  of  beeswax  and  rosin  melted  together  to  the  inside  of  the  upper  part  of 
the  bell  glass.  Put  the  bell  glass  on  a  large  plate  or  sheet  of  glass  on  which 
lies  wet  paper  to  keep  the  air  moist.  Note  whether  or  not  the  seedlings  form 
hypocotyl  arches,  and,  if  so,  whether  the  arch  is  more  or  less  perfect  than 
that  formed  by  seedlings  growing  in  earth,  sand,  or  sawdust. 


28     STKUCTUKE  AND  rilYSlOLOGY   OF   SEED  PLANTS 

EXPERIMENT  XII 

The  permanganate  test,  to  distinguish  root  from  hypocotyl.  Make  a  solu- 
tion of  potassium  permanganate  in  water  by  adding  about  4  parts,  by 
weight,  of  the  crystallized  permanganate  to  100  parts  of  water.  Drop  into 
the  solution  seedlings  of  all  the  kinds  that  have  been  so  far  studied,  each 
in  its  earliest  stage  of  germination  (that  is,  when  the  root,  or  hypocotyl, 
has  pushed  out  of  the  seed  half  an  inch  or  less),  and  also  at  one  or  two  sub- 
sequent stages.  After  the  seedlings  have  been  in  the  solution  from  three  to 
five  minutes,  or  as  soon  as  the  roots  are  considerably  stained,  pour  off  (and 
save)  the  solution  and  rinse  the  plants  with  plenty  of  clear  water.  Sketch 
one  specimen  of  each  kind,  coloring  the  brown-stained  part,  which  is  root, 
in  some  way  so  as  to  distinguish  it  from  the  unstained  hypocotyl.  Note 
particularly  how  much  difference  there  is  in  the  amount  of  lengthening  in 
the  several  kinds  of  hypocotyl  examined.  Decide  whether  the  peg  of  the 
squash  seedling  is  an  outgrowth  of  the  hypocotyl  or  of  the  root. 

EXPERIMENT  XIII 

In  what  portions  of  the  root  does  its  increase  in  length  take 
place?  *  *  Sprout  some  peas  on  moist  blotting  paper  in  a  loosely 
covered  tumbler.  When  the  roots  are  one  and  a  half  inches  or 
more  long,  mark  them  along  the  whole  length  with  equidistant 
dots  made  with  a  bristle  dipped  in  waterproof  India  ink,  or  a 
fine  inked  thread  stretched  on  a  little  bow  of  whalebone  or 
brass  wire. 

Fasten  the  peas  with  pins  to  moist  blotting  paper  placed  in  a 
vertical  position  under  a  bell  glass  or  an  inverted  battery  jar,  and 
examine  the  roots  at  the  end  of  twenty-four  hours  to  see  along 
what  portions  their  length  has  increased ;  continue  observations 
on  them  for  several  days. 

References.    Detmer-Moor,  9  ;  Pfeffer-Ewart,  31,  II ;  Darwin 
and  Acton,  11. 

17.  Review  sketches.  Make  out  a  comparison  of  the  early  life 
histories  of  all  the  other  seedlings  studied,  by  arranging  in  par- 
allel columns  a  series  of  drawings  of  each,  like  those  of  Principles, 
Fig.  8,  but  in  vertical  series,  the  youngest  of  each  at  the  top,  thus : 


ROOTS 


29 


First  stage 


Second  stage 


Third  stage 


Fourth  stage 


Bean 

Pea 

Corn 

> 

Fifth  stage 


Discuss  their  resemblances  and  differences. 


ROOTS 

18.  Growth  and  microscopical  examination  of  water  roots.  *  * 
A.  Place  some  vigorous  cuttings  of   Trade  scant  la,  which  can 
usually  be  obtained  of  a  gardener  or  florist,  in  a  beaker  or 


30     STRUCTURE  AND  PHYSIOLOGY  OF   SEED  PLANTS 

jar  of  water.  The  jar  should  be  as  thin  and  transparent  as 
possible,  and  it  is  well  to  get  a  flat-sided  rather  than  a  cylin- 
drical one.  Leave  the  jar  of  cuttings  in  a  sunny,  warm  place. 
B.  As  soon  as  roots  have  developed  at  the  nodes,  and  reached 
the  length  of  three  quarters  of  an  inch  or  more,  arrange  a 
microscope  in  a  horizontal  position  (Fig.  1)  and  examine  the 


Fig.  1.    Microscope  on  ring  stand 

tip  and  adjacent  portion  of  one  of  the  young  roots  with  a 
power  of  from  twelve  to  twenty  diameters.    Note : 

(1)  The  root  cap,  of  loosely  attached  cells. 

(2)  The  central  cylinder. 

(3)  The  cortical  portion,  a  tubular  part  inclosing  the 
solid  central  cylinder. 

(4)  The  root  hairs,  which  cover  some  parts  of  the  outer 
layer  of  the  cortical  portion  very  thickly.  Observe 
particularly  how  far  toward  the  tip  of  the  root  the 
root  hairs  extend,  and  where  the  youngest  ones 
are  found. 


ROOTS  31 

Make  a  drawing  to  illustrate  all  the  points  above  suggested 
(1-4).  Make  a  careful  study  of  longitudinal  sections  through 
the  centers  of  the  tips  of  very  young  roots  of  the  hyacinth  or 
the  "  Chinese  sacred  lily."  ^    Sketch  one  section. 

Make  a  study  of  the  roots  of  any  of  the  common  duckweeds, 
growing  in  nutrient  solution  (No.  1,  Exp.  XV)  in  a  jar  of  water 
under  a  bell  glass,  and  note  the  curious  root  pockets,  which  here 
take  the  place  of  root  caps. 

References.  Strasburger-Hillhouse,  6 ;  Strasburger,  Noll, 
Schenck,  Karsten,  1. 

19.  Structure  of  the  central  cylinder  of  a  monocotyledonous  root.*  *  Cut  thin 
cross  sections  of  the  adventitious  roots  of  onion  or  hyacinth  near  their  bases.  2 
Examine  these  in  water  with  a  power  of  two  hundred  or  more  diameters. 

The  central  cylinder  or  stele  shows  in  the  cross  section  as  a  nearly  circular 
area  containing  a  few  large  openings  and  many  smaller  ones.  The  largest  open- 
ings are  usually  only  one  or  two  in  number  and  represent  the  large  vessels 
cut  across.  These  are  tubes  with  a  diameter  of  3!^  to  ^^J^  of  an  inch,  with 
iadder-like  markings  (seen  only  in  the  longitudinal  section)  on  their  walls. 
Radiating  away  from  these  are  the  openings  of  (in  the  onion)  six  other  ves- 
sels of  about  half  the  diameter  of  the  central  vessels  and  with  similar  mark- 
ings. Just  outside  of  each  of  the  six  vessels  is  an  irregular  group  of  much 
smaller  vessels  with  spiral  markings  (seen  on  longitudinal  section).  The 
openings  of  the  vessels  form  on  the  cross  section  of  the  central  cylinder  an 
irregular  six-rayed  star,  and  the  spaces  between  the  rays  are  mainly  filled  by 
sieve  tubes  or  soft  bast^  separated  from  the  vessels  of  the  wood  system  by 
parenchyma  cells.  The  outermost  portion  of  the  central  cylinder  consists  of 
a  single  layer  of  cells  constituting  the  pericijcle,  and  this  is  surrounded  by 
the  innermost  layer  of  the  primary  cortex,  the  endodermis. 

Reference.    Strasburger-Hillhouse,  6. 

20.  Structure  of  the  dicotyledonous  root ;  secondary  thickening. ^  The  struc- 
ture of  very  young  dicotyledonous  roots  is  often  similar  in  most  respects 
to  that  of  the  onion  root  (Sec.  19).*    Secondary  thickening  {Principles,  Sec.  80) 

1  Narcissus  Tazetta,  var.  orientalis. 

2  These  roots  may  be  obtained  from  an  onion  or  a  hyacinth  bulb  set  in  a  tum- 
blerful of  water  and  left  in  a  warm  place  until  the  roots  are  well  developed.  They 
may  also  be  taken  from  hyacinth  plants  urowing:  in  pots,  by  inverting  the  latter, 
removine^  the  contents,  and  replacing  the  plant  when  the  needed  material  has  been 
secured  from  it. 

3  This  section  may  to  advantage  be  deferred  until  after  Sec.  31. 

*  Good  materials' for  study  are  roots  of  Ranunculus,  bean,  or  (very  young) 
grapevines. 


S'2     STRUCTUKK   AND   PHYSIOLOGY  OF   SEED  PLANTS 

soon  occurs  in  the  roots  of  dicotyledonous  trees  and  shrubs,  and  the  structure 
of  such  roots  considerably  resembles  that  of  the  stem,  except  that  pith  is 
frequently  lacking. 

With  the  lens  examine  cross  sections  of  large  roots  of  any  hardwood  tree. 
Note  the  annual  rings  of  wood  and  their  porosity,  due  to  the  presence  of 
many  and  large  vessels.  The  cortical  part  sometimes  (as  in  sassafras)  forms 
a  thick  bark. 

With  the  microscope  examine  thin  cross  sections,  stained  with  phloro- 
glucin  (Sec.  12,  D),  of  the  tap  root  of  a  seedling  hardwood  tree  not  more 
than  a  year  old.i  Use  first  l.p.,  then  m.p.  Note  the  division  of  the  root 
into  a  cortical  region  or  bark,  wood,  and  (sometimes)  pith.  Note  the  relatively 
small  amount  of  wood  in  the  younger  portions  of  the  root,  increasing  in  the 
older  parts.  Make  drawings  to  illustrate  this  point.  Make  a  drawing  of  a 
(luarter  or  less  of  one  of  the  older  sections,  showing  the  distribution  of  mate- 
rial from  center  to  exterior.  In  your  drawing  color  the  lignified  hard-bast 
fibers  of  the  bark  (Sec.  29,  C)  and  the  wood  fibers,  to  distinguish  them  from  the 
non-fibrous  parenchyma  which  makes  up  much  of  the  bulk  of  the  young  root. 

If  the  material  was  collected  in  the  autumn  or  winter,  test  a  section  with 
iodine  solution  for  starch,  and  if  any  is  found  describe  its  distribution. 

References.     Strasburger-Hillhouse,    6 ;    Strasburger,    Noll,    Schenck, 
Karsten,  1 ;  Tschirch,  83. 

21.  Examination  of  a  fleshy  root.  Cut  a  parsnip  across  below 
the  middle,  and  stand  the  cut  end  of  the  upper  part  in  eosin  solu- 
tion (Sec.  169)  for  twenty-four  hours. 

A.  Examine  by  slicing  off  successive  portions  from  the  upper 
end.  Sketch  some  of  the  sections  thus  made.  Cut  one  pars- 
nip lengthwise  and  sketch  the  section  obtained.  In  what 
portion  of  the  root  did  the  colored  liquid  rise  most  readily  ? 
The  ring  of  red  marks  the  exterior  of  the  central  cylinder 
in  contact  with  the  cortical  portion.  To  which  does  the 
main  bulk  of  the  parsnip  belong  ? 

B.  Cut  thin  transverse  sections  from  an  eosin-stained  parsnip 
and  notice  how  the  medullary  rays  run  out  into  the  cortical 
portion,  and  in  those  sections  that  show  it  find  out  where 
the  secondary  roots  arise. 

1  These  may  be  pl:iiite(i  lor  the  purpose,  but  usually  it  is  easy  to  find  plenty  of 
young  seedling  cherries,  birches,  elms,  ashes,  maples,  etc. 


MINERAL   SUB8TAx\Ci:s   Hi:(^UIRED  BY    PLANTS       33 

C.  If  possible,  peel  off  the  cortical  portion  from  one  stained 
root  and  leave  the  central  cylinder  with  the  secondary  roots 
attached.  Stain  one  section  with  iodine  and  sketch  it. 
Where  is  the  starch  of  this  root  mainly  stored  ? 

D.  Test  some  bits  of  parsnip  for  proteids  by  boiling  them  for 
a  minute  or  two  with  strong  nitric  acid. 

What  kind  of  plant  food  does  the  taste  of  cooked  parsnips 
indicate  ?  [  On  no  acconnt  taste  the  hits  which  have  been 
boiled  in  the  poisonous  filtric  acid.'] 

EXPERIMENT  XIV 

Percentage  of  water  in  the  plant  body.  Take  any  such  soft  portions  of  seed 
plants  as  the  roots  of  carrots  or  turnips,  shoots  of  asparagus,  and  leaves  of 
lettuce  or  spinach,  or  cut  off  a  green  herbaceous  plant  at  the  level  of  the 
ground.  iSlice  the  roots  and  stems  as  thin  as  possible  and  pick  the  leaves  to 
pieces.  Weigh  out  convenient  portions  at  once  to  avoid  drying,  place  each 
portion  in  a  water  bath,  and  heat  until  no  further  loss  of  weight  takes  place. 
It  will  save  much  time  and  render  the  experiment  more  accurate  if  the 
materials  are  in  each  case  kept  in  a  shallow  vessel,  such  as  a  large  watch 
glass,  throughout  the  process  of  drying  and  the  weighings.  Finally  calculate 
from  the  loss  of  weight  the  percentage  of  water  originally  present. 

EXPERIMENT  XV 

What  mineral  substances  are  required  by  ordinary  seed  plants  ?  *  * 
A.  Prepare  a  nutrient  solution  (No.  1)  containing   for  every  1500  parts 
by  weight  (grams)  of  water ^  the  following  amounts  of  salts: 

Grams 

Calcium  nitrate 2 

Potassium  chloride ^ 

Magnesium  sulphate ^ 

Acid  potassium  phosphate  (KH2  PO4) ^ 

Ferric  chloride  solution a  few  drops 

Prepare  several  glass  cylinders  of  the  capacity  of  a  pint  or  more  by 
rinsing  out  with  strong  nitric  acid  and  then  with  plenty  of  water. 

1  Distilled  water  which  has  been  prepared  in  a  ^lass,  porcelain,  or  block  tin 
distilling  apparatus  and  then  aerated  by  shaking  up  with  air  should  be  used. 
Very  pure  raiu  water  collected  from  a  thoroughly  washed  root  will  answer 
equally  well. 


34      STRUCTURE  AND  PHYSIOLOGY  OF   SEED  PLANTS 

B.  Make  another  nutrient  solution  (No.  2)  like  No.  1,  but  without  iron  ; 
another  (No.  3)  containing  the  same  ingredients  as  No.  1,  except  the  cal- 
cium nitrate,  for  which  one  gram  of  calcium  sulphate  is  to  be  substi- 
tuted; and  another  (No.  4)  like  No.  1,  except  that  acid  sodium  phosphate 
is  to  be  substituted  for  the  acid  potassium  phosphate. 

C.  Place  in  each  jar  a  vigorous  young  wheat  seedling  with  only  its  roots 
submerged,  or  a  cutting  of  Tradescantia.  Cover  each  jar  with  a  piece  of 
pasteboard  wrapped  around  the  glass  so  as  to  exclude  light  from  the 
solution  and  put  all  the  jars  in  a  warm  place  but  not  in  full  sunlight. 
Change  the  nutrient  solution  every  week  and  continue  the  culture  for 
four  or  five  weeks.  If  the  roots  seem  dirty  and  slimy,  allow  the  plants 
to  stand  for  a  day  or  two  at  a  time  with  the  roots  in  distilled  water  or 
a  weak  solution  of  calcium  sulphate. 

D.  At  the  end  of  the  period  sketch  all  the  plants  and  label  as  follows  : 

1.  Culture  in  full  nutrient  solution. 

2.  Culture  without  iron. 

3.  Culture  without  nitrogen. 

4.  Culture  without  potassium. 

What  conclusions  can  you  draw  from  the  experiment  ? 
References.    Detmer-Moor,  9 ;  Pfeffer-Ewart,  31,  I ;  Peirce,  32. 

EXPERIMENT  XVI 

Effect  of  diminished  temperature  on  absorption  of  water  by  roots. 

A.  Transplant  a  tobacco  seedling  about  four  inches  high  into  rich  earth 
contained  in  a  narrow,  tall  beaker  or  very  large  test  tube  (not  less 
than  1^  inch  in  diameter  and  six  inches  high). 

B.  When  the  plant  has  begun  to  grow  again  freely  in  a  warm,  sunny  room, 
insert  a  chemical  thermometer  into  the  earth  ;  this  can  best  be  done  by 
making  a  hole  with  a  sharp,  round  stick,  pushed  nearly  to  the  bottom  of 
the  tube,  and  then  putting  the  thermometer  in  the  place  of  the  stick. 
Water  the  plant  well,  and  then  set  the  tube  in  a  jar  of  pounded  ice  which 
reaches  nearly  to  the  top  of  the  tube.  Note  the  temperature  of  the  earth 
just  before  placing  it  in  the  ice.  Cover  the  ice  with  cotton  batting  or  a 
piece  of  flannel  so  that  the  stem  and  leaves  of  the  plant  will  not  be 
chilled  by  the  proximity  of  the  ice. 

C.  Observe  whether  the  leaves  of  the  seedling  wilt,  and  if  so,  at  what 
temperature  the  wilting  begins. 

D.  Finally,  remove  the  tube  from  the  ice  and  place  it  in  warm  water 
(about  80°  F.  or  27°  C).  Observe  the  effect  and  note  the  temperature 
at  which  the  plant,  if  wilted,  begins  to  revive, 


DOWNWARD  GROWTH   OF  THE  ROOT 


35 


E.  Find  an  average  between  the  wilting  temperature  and  the  reviving 
temperature.  For  what  does  this  average  stand  ?  Repeat  the  experi- 
ment with  oat  seedlings. 

Reference.     Pfeffer-Ewart,  31,  I. 

EXPERIMENT  XVH 

Do  all  parts  of  the  root  of  the  Windsor  bean  seedling  bend  downward  alike  ? 
Fasten  some  sprouting  Windsor  beans  with  roots  about  an  inch  in  length  to 
the  edges  of  a  thick  disk  of  pine  wood  or  other  soft  wood  in  a  soup  plate  partly- 
full  of  water  and  cover  them  with  a  low  bell  jar. 

Steel  pins  run  through  the  cotyledons,  as  in  Fig.  2,  will  hold  the  beans  in 
place.  Mark  the  roots,  as  in  Exp.  XIH,  to  see  in  what  region  the  bending 
occurs  ;  that  is,  whether  in  the  older  part  or  by  the  addition  of  new  material 
at  the  tip.  When  the  roots  have  begun  to  point  downward  strongly,  turn 
most  of  the  beans  upside  down  and  pin  them  in  the  reversed  position.  If 
you  choose,  after  a  few  days  reverse  them  again.  Make  sketches  of  the  vari- 
ous forms  that  the  roots  assume  and  discuss  these. 

References.    Detmer-Moor,  9;  Pfeffer-Ewart,  81,  HI. 


EXPERIMENT  XVIII 

Does  the  Windsor  bean  root  tip  press  downward  with  a  force  greater  than  its 
own  weight?  Arrange  a  sprouted  bean  as  shown  in  Fig.  2,i  selecting  one 
that  has  a  root  about  twice 
as  long  as  the  diameter  of 
the  bean  and  that  has 
grown  out  horizontally, 
having  been  sprouted  on  a 
sheet  of  wet  blotting  paper. 
The  bean  is  pinned  to  a 
cork  that  is  fastened  with 
beeswax  and  rosin  mixture 
to  the  side  of  a  little  trough 
or  pan  of  glass  or  glazed 
earthenware.  The  pan  is 
filled  half  an  inch  or  more 
with  perfectly  clean  mer- 
cury, and  on  top  of  the  mercury  is  a  layer  of  water.  The  whole  is  closely 
covered  by  a  large  tumbler  or  a  bell  glass.  Allow  the  apparatus  to  stand 
until  the  root  has  forced  its  way  down  into  the  mercury.   Then  run  a  slender 

1  Or  see  Ganong,  10. 


Fig.  2.  A  sprouting  Windsor  bean  pushing  its 
root  tip  into  mercuiy 

s,  seed;  r,  root;  w,  layer  of  water;  m,  mercury 
After  Sachs 


36     STRUCTURE  AND   PHYSIOLOGY   OF   SEED  PLANTS 

needle  into  tlie  root  at  the  level  of  the  mercury  (to  mark  the  exact  level), 
withdraw  the  root,  and  measure  the  length  of  tlie  part  submerged  in  mercury. 
To  see  whether  this  part  would  have  stayed  under  by  virtue  of  its  own  weight, 
cut  it  off  and  lay  it  on  the  mercury.  Push  it  under  with  a  pair  of  steel  for- 
ceps and  then  let  go  of  it.    What  does  it  do  ? 

EXPERIMENT  XIX 

What  causes  the  root  to  go  downward  ? 

A.  Pin  some  soaked  Windsor  beans  to  a  large  flat  cork,  cover  them  with 
thoroughly  moistened  chopped  peat  moss,  and  cover  this  with  a  thin 
glass  crystallizing  dish.    Set  the  cork  on  edge. 

B.  Prepare  another  cork  in  the  same  way,  attach  it  to  a  clinostat,  and 
keep  it  slowly  revolving  in  a  vertical  position  for  from  three  to  five 
days.  Compare  the  directions  taken  by  the  roots  on  the  stationary  and 
on  the  revolving  cork. 

Rekkrences.     Ganong,  10  ;  Pfeffer-Ewart,  31,  III. 

22.  Propagation  by  means  of  roots.  Bury  a  sweet  potato  or  a 
dahlia  root  in  damp  sand  and  watch  the  development  of  sprouts 
from  adventitious  buds.  One  sweet  potato  will  produce  several 
crops  of  sprouts,  and  every  sprout  may  be  made  to  grow  into  a 
new  plant.  It  is  in  this  way  that  the  crop  is  started  wherever 
the  sweet  potato  is  grown  for  the  market. 


SOME  PROPERTIES   OF  CELLS  AND  THEIR 
FUNCTIONS   IN   THE  ROOT 

EXPERIMENT  XX 

Osmosis  as  shown  in  an  egg. 

A.  Cement  to  the  smaller  end  of  an  egg  a  bit  of  glass  tubing  about  six 
inches  long  and  about  three  sixteenths  of  an  inch  in  inside  diameter.  A 
mixture  of  equal  parts  of  beeswax  and  rosin  melted  together  makes 
the  best  cement  for  this.  Chip  away  part  of  the  shell  from  the  larger 
end  of  the  egg,  place  it  in  a  wide-mouthed  bottle  or  a  small  beaker  full 
of  water  (as  shown  in  Principles,  Fig.  28),  and  then  very  cautiously 
pierce  a  hole  through  the  upper  end  of  the  eggshell  by  pushing  a 
knitting  needle  or   wire  down  through  the  glass  tube.    AVatch   the 


EXPERIMENTS   ON   OSMOSIS  37 

apparatus  for  some  hours  and  note,  any  change  in  the  contents  of  the 
tube  or  the  beaker. i    Explain. 

The  rise  of  liquid  in  the  tube  is  evidently  due  to  water  making  its 
way  through  the  thin  membrane  which  lines  the  eggshell,  although 
this  membrane  contains  no  pores  visible  even  under  the  microscope. 

B.  An  alternative  experiment  is  to  fasten  a  pig's  bladder  or  a  diffusion 
shell  (obtainable  of  dealers  in  chemical  and  physical  apparatus)  to  the 
end  of  a  glass  tube  six  or  eight  feet  long.  For  a  ^-inch  (16-mm.) 
diffusion  shell  the  tube  should  be  |-in.  outside  diameter;  for  the 
bladder  a  tube  must  be  chosen  that  barely  enters  the  opening  in  it. 
A  tight  joint  is  more  certainly  secured  by  using  a  tube  a  little  smaller 
than  is  needed  to  enter  the  opening  in  the  shell  or  bladder,  slipping 
over  the  tube  a  bit  of  rubber  tubing  an  inch  or  more  long,  inserting 
this  in  the  shell  and  wiring  it  tightly  with  rather  fine  copper  wire. 
Fasten  the  tube  upright,  with  the  diffusion  membrane  submerged  in  a 
large  jar  of  water,  and  pour  into  the  open  end  of  the  tube  enough 
molasses  to  remain  visible  above  the  diffusion  membrane.  A  rather 
large  tube  may  be  filled  through  a  slender  funnel,  taking  pains  not  to 
let  the  molasses  stick  to  the  sides  as  it  descends.  A  narrow  tube  must 
be  filled  before  tying  into  the  neck  of  the  bladder,  the  free  end  of  the 
tube  corked,  and  the  other  end  then  tied  in  place.  Note  any  change  of 
level  in  the  molasses  in  the  tube. 2 

References.    Ganong,  10;  Detmer-Moor,  9;  Pfeffer-Ewart,  31,  I. 

EXPERIMENT  XXI 

Result  of  placing  sugar  on  a  begonia  leaf.  Put  a  little  powdered 
sugar  on  the  upper  surface  of  a  thick  begonia  leaf  under  a  small 
bell  glass.  Put  another  portion  of  sugar  on  a  bit  of  paper  along- 
side the  leaf.  Watch  for  several  days.  Explain  the  results.  The 
ivpper  surface  of  this  leaf  contains  no  pores,  even  of  micro- 
scopic size. 

STEMS 

23.  The  horse-chestnut  or  buckeye  twig.^  *  Procure  a  twig  of 
horse-chestnut  eighteen  inches  or  more  in  length.  Make  a  careful 
sketch  of  it,  trying  to  bring  out  the  following  points : 

A.  The  general  character  of  the  bark. 

1  Testing  the  contents  of  the  beaker  with  a  solution  of  nitrate  of  silver  will  then 
show  the  presence  of  more  common  salt  than  is  found  in  ordinary  water. 

2  A  still  more  instructive  experiment  is  that  on  plasmolysis  of  the  Spirogyra 
cell  (Sees.  56,  D,  and  57,  C). 


38      STRUCTURE  AND  PHYSIOLOGY  OF  SEED  PLANTS 

B.  The  large  horseshoe-shaped  scars  and  the  number  and  posi- 
tion of  the  dots  on  these  scars.  Compare  a  scar  with  the 
base  of  a  leafstalk  furnished  for  the  purpose. 

C.  The  ring  of  narrow  scars  around  the  stem  in  one  or  more 
places,  and  the  different  appearance  of  the  bark  above  and 
below  such  a  ring.'^  Compare  these  scars  with  those  left 
after  removing  the  scales  of  a  terminal  bud. 

D.  The  buds  at  the  upper  margin  of  each  leaf  scar  and  the 
strong  terminal  bud  at  the  end  of  the  twig.  The  dots  on  the 
leaf  scars  mark  the  position  of  the  ducts  and  wood  cells  in 
the  fibro-vascular  bundles  which  run  from  the  wood  of  the 
branch  through  the  leafstalk  up  into  the  leaf. 

E.  The  flower-bud  scar,  a  concave  impression  to  be  found  in 
the  angle  produced  by  the  forking  of  two  twigs,  which  form, 
with  the  branch  from  which  they  spring,  a  Y-shaped  figure. 

¥.  The  place  of  origin  of  the  twigs  on  the  branch  (on  a  branch 
larger  than  the  twig  handed  round  for   individual  study); 
make  a  separate  sketch  of  this. 
The  portion  of  a  stem  which  originally  bore  any  pair  of  leaves 
is  a  ?iode,  and  the  portions  between  the  nodes  are  internodes. 

Describe  briefly  in  writing  alongside  the  sketches  any  observed 
facts  which  the  drawings  do  not  show. 

If  your  twig  was  a  crooked,  rough-barked,  and  slow-growing 
one,  exchange  it  for  a  smooth,  vigorous  one,  and  note  the  differ- 
ences. Or  if  you  sketched  a  quickly  grown  shoot,  exchange  for 
one  of  the  other  kind. 

Questions.  1.  How  many  inches  did  your  twig  grow  during 
the  last  summer  ?  How  many  during  the  summer  before  ? 
How  do  you  know  ?  How  many  years  old  is  the  whole  twig 
given  you  ? 
2.  How  were  the  leaves  arranged  on  the  twig  ?  How  many 
leaves  were  there  ?    Were  they  all  of  the  same  size  ? 

1  Maple,  box  elder,  or  lilac  may  be  used,  though  they  are  not  nearly  as  good. 
Instead  of  poplar,  as  described  in  the  next  section,  basswood,  any  kind  of  hickory, 
butternut,  black  walnut,  oak,  or  willow  will  do.  The  rings  are  especially  well 
shown  by  cherry,  apple,  pear,  cottonwood,  or  aspen. 


STEMS  AND  STEM  STRUCTURE  39 

3.  What  has  the  mode  of  branching  to  do  with  the  arrangement 

of  the  leaves  ?    with  the  position  of  the  flower-bud  scars  ? 
24.  Twig  of  poplar. 

A.  Sketcli  a  vigorous  young  twig  of  poplar  for  of  liickory, 
magnolia,  or  tulip  tree)  in  its  winter  condition,  noting  par- 
ticularly the  respects  in  which  it  differs  from  the  horse- 
chestnut.  Describe  in  writing  any  facts  not  shown  in  the 
sketch.  Notice  that  the  buds  are  not  opposite,  nor  is  the 
next  one  above  any  given  bud  found  directly  above  it,  but 
part  way  round  the  stem  from  the  position  of  the  first  one. 

B.  Ascertain,  by  studying  several  twigs  and  counting  around, 
which  bud  is  above  the  first  and  how  many  turns  round  the 
stem  are  made  in  passing  from  the  first  to  the  one  directly 
above  it.^ 

C.  Observe  with  especial  care  the  difference  between  the  poplar 
and  the  horse-chestnut  in  mode  of  branching,  as  shown  in  a 
large  branch  provided  for  the  study  of  this  feature. 


STRUCTURE  OF  THE  STEM 

Stem  of  Moxocotyledoxous  Plants 

25.  Gross  structure  of  the  corn  stem.*  *  Refer  to  the  sketches  of 
the  corn  seedling  to  recall  the  early  history  of  the  corn  stem. 

A.  Study  the  external  appearance  of  a  piece  of  corn  stem  or 
bamboo  two  feet  or  more  in  length.  Note  the  character  of 
the  outer  surface.  Sketch  the  whole  piece  and  label  the 
enlarged  nodes  and  the  nearly  cylindrical  internodes. 

B.  Cut  across  a  corn  stem  and  examine  the  cut  surface  with 
the  lens.  iSfake  some  sections  as  thin  as  they  can  be  cut 
and  examine  with  the  lens  (holding  them  up  to  the  light) 
or  with  a  dissecting  microscope.  Note  the  firm  rind  com- 
posed of  the  epidermis  and  the  underlying  tissue,  the  large 

1  This  may  be  made  clearer  by  winding  a  thread  about  the  twig,  making  it 
touch  the  base  of  each  bud. 


40     S'JRrc'nKK    AM)    IMIYSlOLOdV    OF    SKKD    PLANTS 

mass  of  pith  composing  the  main  bulk  of  the  stem,  and  the 
many  little  harder  and  more  opaque  spots,  which  are  the 
cut-off  ends  of  the  woody  threads  known  as  tihro-vascular 
bundles. 

C.  Split  a  portion  of  the  stem  lengthwise  into  thin,  translucent 
slices,  and  notice  whether  the  bundles  seem  to  run  straight  up 
and  down  its  length ;  sketch  the  entire  section  (  X  2).  Every 
fibro-vascular  bundle  of  the  stem  passes  outward  through 
some  node  in  order  to  connect  with  some  fibro-vascular 
bundle  of  a  leaf.  Knowing  this  fact,  the  student  would 
expect  to  find  the  bundles  bending  out  of  a  vertical  position 
more  at  the  nodes  than  elsewhere.  Can  this  be  seen  in  the 
stem  examined?  Observe  the  thickening  at  the  nodes,  and 
split  one  of  these  lengthwise  to  show  the  tissue  within  it. 

D.  Compare  with  the  corn  stem  a  piece  of  palmetto  and  a  piece 
of  cat  brier  (Smilax  rotundifolla,  S.  hispida,  etc.),  and  notice 
the  similarity  of  structure.  Compare  also  a  piece  of  rattan 
and  of  bamboo. 

Minute  structure. 

E.  Stain  a  thin  cross  section i  with  phloroglncin  (Sec.  12,  D)  and  sketch  with 
m.p.  one  of  the  larger  bundles  (some  distance  in  from  the  rind).  In  your 
drawing  color  the  stained  portions,  which  represent  the  lignified  scleren- 
chyma  fibers.    Look  for  stained  rigid  tissue  (sclerenchyma)  in  the  rind. 

F.  Cut  several  very  thin  longitudinal  sections  from  a  piece  of  stem  not  more 
than  one-fourth  to  one-third  inch  long,  split  through  the  middle.  Stain 
with  phloroglncin  and  make  a  drawing  of  the  best  bundle  found.  Note 
the  two  kinds  of  vessels,  or  vessel-like  tracheids,  some  with  spiral 
tJireads  lining  the  interior,  and  others  with  transverse  rings.  Separate 
rings  are  often  seen  detached  from  their  vessels  and  beautifully  stained 
by  the  phloroglncin. 

Hefekences.  Strasburger-Hillhouse,  (3 ;  Strasburger,  Noll, 
Schenck,  Karsten,  1. 

A  more  complicated  kind  of  monocotyledonous  stem  structure 
can  be  studied  to  advantage  in  the  surgeons'  splints  cut  from 
yucca  stems  and  sold  by  dealers  in  surgical  supplies. 

1  Asparagus  stem  may  also  be  used. 


STKUCTL'RK   OF  STEMS  41 

Stem  of  Dicotyledonous  Plants 

26.  Gross  structure  of  an  annual  dicotyledonous  stem.** 

A.  Study  the  external  appearance  of  a  piece  of  sunflower  stem 
several  inches  long.    If  it  shows  distinct  nodes,  sketch  it. 

B.  Examine  the  cross  section  with  the  lens  and  sketch  it. 
After  your  sketch  is  finished  compare  it  with  Principles,  Fig. 
56,  which  probably  shows  more  details  than  your  drawing, 
and  label  the  parts  shown  as  they  are  labeled  in  that  figure. 

C.  Split  a  short  piece  of  the  stem  lengthwise  through  the 
center  and  study  the  split  surface  with  the  lens.  Take  a 
sharp  knife  or  a  scalpel  and  carefully  slice  and  then  scrape 
away  the  bark  until  you  come  to  the  outer  surface  of  a 
bundle. 

D.  Examine  a  vegetable  sponge  {Luffa),  sold  by  druggists, 
and  notice  that  it  is  simply  a  network  of  fibro-vascular 
bundles.  It  is  the  skeleton  of  a  tropical  seed  vessel  or  fruit, 
very  much  like  that  of  the  wild  cucumber  common  in  the 
central  states,  but  a  great  deal  larger. 

Structure  of  bark.  The  different  layers  of  the  bark  cannot  all  be  well  recog- 
nized in  the  examination  of  a  single  kind  of  stem.     With  lens  examine  : 

E.  The  cork  which  constitutes  the  outer  layers  of  the  bark  of  cherry  or 
birch  branches  two  or  more  years  old.  Sketch  the  roundish  or  oval 
lenticels  on  the  outer  surface  of  the  bark.   How  far  in  do  they  extend  ? 

y.  The  green  layer  of  bark  as  shown  in  twigs  or  branches  of  Forsythia, 

cherry,  alder,  box  elder,  wahoo,  or  willow. 
G.  The  white,  fibrous  inner  layer,  known  as  hard  bast,  of  the  bark  of  elm, 

leatherwood,  or  basswood. 

27.  Minute  structure  of  the  ordinary  dicotyledonous  stem.  Cut  thin  cross 
sections  of  the  stem  of  one  of  the  perennial  species  of  sunflower  (Helianihus), 
or  any  large  composite.  Stain  by  immersing  for  a  few  seconds  in  a  half- 
saturated  aqueous  solution  of  safranin,  then  wash,  and  examine  in  water, 
first  with  l.p.  and  then  with  m.p.  The  structural  elements  of  the  stem  are 
considerably  differentiated  by  the  stain,  the  outer  layers  of  the  cortex  ap- 
pearing yellowish  brown,  the  hard  bast  magenta,  the  wood  fibers  reddish 
magenta,  and  the  jjith  salmon  color. 

References.  Strasburger-Hillhouse,  6;  Strasburger,  Noll,  Schenck, 
Karsten,  1. 


42     STKUCTURE  AND  PHYSIOLOGY  OF   SEED  PLANTS 

28.  Minute  structure  of  the  climbing  dicotyledonous  stem.*  * 

A.  Study,  first  with  l.p.  and  then  with  m.j).,  thin  cross  sections 
of  clematis  stem^  cut  before  the  end  of  the  first  season's 
growth.  Sketch  tlie  whole  section  without  much  detail,  and 
then  make  a  detailed  drawing  of  a  sector  running  from  cen- 
ter to  circumference  and  just  wide  enough  to  include  one  of 
the  large  bundles.  In  general  label  these  drawings,  as  in 
Figs.  57  and  58  of  the  Principles.     Note  : 

1.  The  general  outline  of  the  section. 

2.  The  number   and   arrangement   of    the    bundles.     (How 
many  kinds  of  bundles  are  there  ?) 

3.  The  comparative  areas   occupied  by  the  woody  part  of 
the  bundle,  and  that  which  belongs  to  the  bark. 

4.  The  way  in  which  the  pith  and  the  outer  bark  are  con- 
nected (and  the  bundles  separated)  by  the  medullary  rays. 

B.  Examine  a  longitudinal  section  of  the  same  kind  of  stem 
to  find  out  more  accurately  of  what  kinds  of  cells  the  pith, 
the  bundles,  and  the  outer  bark  are  built.  Which  portion 
has  cells  that  are  nearly  equal  in  shape,  as  seen  in  both 
sections  ? 

References.  Strasburger-Hillhouse,  6 ;  Strasburger,  Noll, 
Schenck,  Karsten,  1. 

29.  Kinds  of  cells  which  compose  sterns.^  Examine  with  m.p.  these  prepara- 
tions (A-J  below).  Study  very  carefully  each  of  the  required  sections,  find 
in  it  the  kind  of  cell  referred  to,  and  make  a  good  drawing  of  a  group  of 
cells  of  each  kind. 

A.  Very  thin  sections  of  the  outside  layers  of  the  cortex  of  a  potato, 
some  cut  tangential  to  the  outer  surface,  other  sections  cut  at  right 
angles  to  it  {cork). 

B.  Thin  sections  of  the  green  layer  of  the  bark  of  Forsythia^  Evonymus, 
or  box  elder  {Negundo)  {green  cells  of  cortical  parenchyma). 

C.  Thin  cross  sections  and  lengthwise  sections  of  the  inner  bark  of 
linden  twigs.    Test  with  phloroglucin  {hard  bast).^ 

1  Clematis  virginiana  is  simpler  in  structure  than  some  of  the  other  woody 
species.  Aristolochia  or  Menispennum  sections  will  do  very  well.  If  unmounted 
sections  are  studied,  stain  with  phloroolucin  (Sec.  12,  D).     2  gee  also  Sec.  138,  B. 

s  Both  hard-bast  fibers  and  wood  fibers  are  known  as  sclerenchym,a,  but  they 
differ  somewhat  in  appearance  and  much  in  location. 


STEM  STRUCTURE  43 

i).  Lengthwise  sections  of  the  stem  of  squash  or  cucumber  plants  {sieve 
cells  or  soft  bast). 

E.  Thin  cross  sections  of  young  twigs  of  pine  or  oak,  collected  and  pre- 
served in  late  summer  {cambium). 

F.  Thin  cross  sections  and  lengthwise  sections  of  apple,  plum,  maple,  or 
box-elder  wood.    Test  with  phloroglucin  {wood fibers).'^ 

G.  Thin  lengthwise  sections  of  any  coniferous  wood.  Test  with  phloro- 
glucin {tracheids). 

H.  Thin  lengthwise  sections  of  the  stem  of  castor-oil  plant  {Ricinus)  or 

of  banana  fruit  stalks  {vessels). 
I.  Thin  lengthwise  radial  sections  of  sycamore,  sassafras,  or  red-cedar 

wood  {wood  parenchyma). 
J.  Thin  sections  of  pith  of  the  stem  of  elder  or  sunflower  {pith  cells). 
References.     Strasburger-Hillhouse,    6 ;     Strasburger,    Noll,    Schenck, 

Karsten,  1. 

30.  Comparative  structure  of  monocotyledonous  and  dicotyledonous  bundles.*  * 
Examine  with  a  power  of  about  150  diameters  : 

A.  The  cross  section  of  a  bundle  of  the  corn  stem  stained  with  phloro- 
glucin. 

B.  The  cross  section  of  a  bundle  of  Aristolochia  stem, 2  stained  with 
phloroglucin. 

Decide  by  referring  to  your  drawings  in  Sees.  25,  28,  which  is  the  outer 
part  of  each  bundle.  Observe  the  number  and  position  of  the  area  made  up 
of  lignified  fibers  (stained  by  the  phloroglucin),  the  cambium  (in  B),  and  the 
sieve  tubes.  These  tubes  are  less  easy  to  identify  than  most  of  the  other 
elements  of  the  bundles,  but  may  be  known  by  their  location :  in  A,  partly 
between  but  mostly  outward  (toward  the  rind)  from  the  pair  of  large 
vessels  ;  in  B,  just  outside  the  cambium  of  the  bundle.  Note  the  general 
resemblance  between  the  two  kinds  of  bundles,  with  the  presence  of  cambium 
in  B  as  much  the  most  important  point  of  difference  between  them. 

31.  The  dicotyledonous  stem,  thickened  by  secondary  growth. 

A.  Cut  off,  as  smoothly  as  possible,  a  small  branch  of  hickory 
and  one  of  white  oak  above  and  belo^v  each  of  the  rings  of 
scars  already  mentioned,  and  count  the  rings  of  wood  above 
and  below  each  ring  of  scars.  How  do  the  numbers  corre- 
spond ?    What  does  this  indicate  ? 

1  Both  hard-bast  fibers  and  wood  fibers  are  known  as  sclerenchyma,  but  they 
differ  somewhat  in  appearance  and  much  in  location. 

2  xhis  section  should  be  made  from  a  young  stem  collected  and  preserved  dur- 
ing the  early  part  of  the  summer. 


44     STRUCTURE  AND   PHYSIOLOGY  OF  SEED   PLANTS 

B.  roiuit  the  rings  of  wood  on  the  cnt-off  ends  of  large  billets 
of  some  of  the  following  woods  :  locust,  chestnut,  sycamore, 
oak,  hickory.  Do  the  successive  rings  of  the  same  tree  agree 
in  thickness  ?  Why  or  why  not  ?  Does  the  thickness  of 
the  rings  appear  uniform  all  the  way  round  the  stick  of 
wood  ?  If  not,  the  reason  in  the  case  of  an  upright  stem 
(trunk)  is  perhaps  that  there  was  a  greater  spread  of  leaves 
on  the  side  where  the  rings  are  thickest  {Principles,  Fig.  76). 
Plant  food,  in  the  case  of  trees,  is  mainly  produced  in  the 
leaves,  and  the  course  through  the  trunk  of  sugar  or  other 
food  in  solution  is  mainly  straight  down  along  the  sieve 
tubes  of  the  young  wood.  This  would  account  for  more  rapid 
growth  on  the  more  leafy  side.  Sometimes  the  inequality 
may  be  because  there  was  unequal  pressure  caused  by  bending 
before  the  wind.  Do  the  rings  of  any  one  kind  of  tree  agree 
in  thickness  with  those  of  all  the  other  kinds  ?  What  does 
this  show? 

C.  In  all  the  woods  examined  look  for : 

1.  Contrasts  in  color  between  the  heartwood  and  the  sapwood. 

2.  The  narrow  lines  running,  in  very  young  stems,  pretty 
straight  from  pith  to  bark  ;  in  older  wood  extending  only  a 
little  of  the  way  from  center  to  bark, — the  medullary  rays. 

3.  The  wedge-shaped  masses  of  wood  between  these. 

4.  The  pores  which  are  so  grouped  as  to  mark  the  divisions 
between  successive  rings.  These  pores  indicate  the  cross 
sections  of  vessels  or  ducts.  Note  the  distribution  of  the 
vessels  in  the  rings  to  which  they  belong,  and  decide  at 
what  season  of  the  year  the  largest  ducts  are  mainly  pro- 
duced. Make  a  careful  drawing  of  the  end  section  of  one 
billet  of  wood,  natural  size. 

D.  Cut  off  a  grapevine  several  years  old  and  notice  the  great 
size  of  the  vessels. 

E.  Examine  the  smoothly  planed  surface  of  a  billet  of  red  oak 
that  has  been  split  through  the  middle  of  the  tree,  and  note 
the  large,  shining  plates  formed  by  the  medullary  rays. 


COURSE  OF   WATER  IN   STEMS  45 

WORK  OF  THE   STEM 
EXPERIMENT   XXII 

Course  of  water  in  stems.*  * 

A.  Cut  some  short  branches  from  an  apple  tree  or  a  cherry 
tree,  and  stand  the  lower  end  of  each  in  eosin  solution ;  try 
the  same  experiment  with  twigs  of  oak,  ash,  or  other  porous 
wood,  and  after  some  hours  ^  examine  with  the  lens  and  with 
the  microscope,  using  l.p.,  successive  cross  sections  of  one  or 
more  twigs  of  each  kind.  Note  exactly  the  portions  through 
which  the  eosin  has  traveled.  Pull  off  the  leaves  from  one 
of  the  stems  after  standing  in  the  eosin  solution,  and  notice 
the  spots  on  the  leaf  scar  through  which  the  eosin  has  trav- 
eled. These  spots  show  the  positions  of  the  leaf  traces,  or 
fibro-vascular  bundles,  connecting  the  stem  and  the  leaf. 

B.  Repeat  with  several  potatoes  cut  crosswise  through  the 
middle. 

C.  Try  also  some  monocotyledonous  stems,  such  as  those  of 
the  lily  or  asparagus. 

D.  For  the  sake  of  comparison  between  roots  and  stems  treat 
any  convenient  root,  such  as  a  parsnip,  in  the  same  way. 

Examine  the  longitudinal  sections  of  some  of  the  twigs,  the 
potatoes,  and  the  roots.  In  drawing  conclusions  about  the 
channels  through  which  the  eosin  has  risen  (those  through 
which  the  newly  absorbed  soil  water  most  readily  travels), 
bear  in  mind  the  fact  that  a  slow  soakage  of  the  eosin  will 
take  place  in  all  directions,  and  therefore  pay  attention  only 
to  the  strongly  colored  spots  or  lines. 

What  conclusions  can  be  drawn  from  this  experiment  as  to 
the  course  followed  by  the  soil  water  ? 

References.  Detmer-Moor,  9  ;  Ganong,  10;  Strasburger,  Noll. 
Schenck,  Karsten,  1  ;  Pfeffer-Ewart,  31,  I. 

1  If  the  twigs  are  leafy  aud  the  rutnu  isi  wariu,  oul\  fiuin  live  to  thirtN  luimites 
may  be  necessary.  The  experiment  may  In-  perfornied  witli  a  translucent-stemmed 
plant  like  Impatten.s  Sultani,  and  the  course  of  the  eosin  watched.  See  Ganong,  10. 


4t)     STRUCTURE  AND  PHYSIOLOGY  OF  SEED  PLANTS 

EXPERIMENT  XXIII 

What  effect  does  loss  of  water  have  on  the  firmness  of  plant 
tissues  ?    How  long  does  it  take  for  the  water  to  be  restored  ? 

A.  Allow  a  fuchsia  or  a  hydrangea^  which  is  growing  in  a 
flowerpot  to  wilt  considerably  for  lack  of  water. 

B.  Then  water  it  freely  and  record  the  time  required  for  the 
leaves  to  begin  to  recover  their  natural  position  and  the 
time  to  recover  fully.  The  time  needed  for  the  leaves  to 
begin  to  resume  their  ordinary  position  is  that  consumed  in 
entering  the  roots  (largely  through  the  root  hairs)  and  push- 
ing upward  through  the  stem  until  the  water  pressure  in  the 
leaves  is  restored  to  its  normal  amount.  Filling  the  leaf 
cells  fuller  of  water  (increasing  their  turgor)  has  the  same 
effect  on  their  firmness  that  inflating  a  football  or  a  bicycle 
tire  does  upon  its  firmness. 

Reference.    Pfeffer  31,  I. 

32.  Examination  of  twigs  for  starch.  Cut  thin  cross  sections  of  twigs  of 
some  common  deciduous  tree  or  shrub  in  its  early  winter  condition,  moisten 
with  iodine  solution,  and  examine  for  starch  with  a  moderately  high  power 
of  the  microscope.  Sketch  the  section  with  a  pencil,  coloring  faintly  the 
starchy  portions  with  blue  ink,  used  with  a  mapping  pen,  and  describe 
exactly  in  what  portions  the  starch  is  deposited. 

33.  A  typical  tuber :  the  potato.  Sketch  the  general  outline  of 
a  potato,  showing  the  attachment  to  the  stem  from  which  it  grew.^ 

A.  Note  the  distribution  of  the  "  eyes."  Are  they  opposite  or 
alternate  ?  Examine  them  closely  with  the  magnifying  glass 
and  then  with  the  lowest  power  of  the  microscope.  What 
do  they  appear  to  be  ? 

B.  If  the  potato  is  a  stem,  it  may  branch ;  look  over  a  lot  of 
potatoes  to  try  to  find  a  branching  specimen.  If  such  a  one 
is  secured,  sketch  it. 

1  Hydrangea  Hortensia. 

2  Examination  of  a  lot  of  potatoes  will  usually  discover  specimens  with  an 
inch  or  more  of  attached  stem. 


TUBERS  A>sD   BULBS  47 

C.  Note  the  little  scale  overhanging  the  edge  of  the  eye,  and 
see  if  you  can  ascertain  what  this  scale  represents. 

D.  Cut  the  potato  across,  and  notice  the  faint  broken  line 
which  forms  a  sort  of  oval  figure  some  distance  inside 
the  skin.  Place  the  cut  surface  in  eosin  solution,  allow  the 
potato  to  stand  so  for  many  liours,  and  then  examine,  by 
slicing  off  pieces  parallel  to  the  cut  surface,  to  see  how  far 
and  into  what  portions  the  solution  has  penetrated.  Refer 
to  the  notes  on  the  study  of  the  parsnip  (Sec.  21),  and  see 
how  far  the  behavior  of  the  potato  treated  with  eosin  solu- 
tion agrees  with  that  of  the  parsnip  so  treated. 

E.  Cut  a  thin  section  at  right  angles  to  the  skin,  and  examine 
with  a  high  power.  Moisten  the  section  with  iodine  solution 
and  examine  again. 

F.  If  possible,  secure  a  potato  which  has  been  sprouting  in  a 
warm  place  for  a  month  or  more  (the  longer  the  better),  and 
look  near  the  origins  of  the  sprouts  for  evidences  of  the  loss 
of  material  from  the  tuber. 

EXPERIMENT  XXIV 

Useof cork.*  =^  Carefully  weigh  a  potato;  then  pare  another 
larger  one,  and  cut  portions  from  it  until  its  weight  is  made 
approximately  equal  to  that  of  the  first  one.  Expose  both  freely 
to  the  air  for  some  days  and  reweigh.  What  does  the  result  show- 
in  regard  to  the  use  of  the  corky  layer  of  the  epidermis? 

34.  Structure  of  a  bulb;  the  onion. 

A.  Examine  the  external  appearance  of  the  onion,  and  observe 
the  thin  membranaceous  skin  which  covers  it.  This  skin 
consists  of  the  broad  sheathing  bases  of  the  outer  leaves 
which  grew  on  the  onion  plant  during  the  summer.  Remove 
these  and  notice  the  thick  scales  (also  formed  from  bases  of 
leaves)  which  make  up  the  substance  of  the  bulb. 

B.  Make  a  transverse  section  of  the  onion  at  about  the  middle, 
and  sketch  the  rings  of  which  it  is  composed.    Cut  a  thin 


48     STRUCTURE  AXD  PHYSIOLOGY  OF   SEED  PLANTS 

section  from  the  interior  of  the  bulb,  examine  with  a  mod- 
erate power  of  the  microscope,  and  note  the  thin-walled  cells 
of  which  it  is  composed. 

C.  Split  another  onion  from  top  to  bottom  and  try  to  find : 

1.  The  broad  flattened  stem  inside  at  the  base. 

2.  The  central  bud. 

3.  The  bulb  scales. 

4.  In  some  onions  (particularly  in  large,  irregular  ones)  the 
bulblets,  or  side  bulbs,  arising  in  the  axes  of  the  scales 

near  the  base. 

D.  Test  the  cut  surfaces  for  starch. 

EXPERIMENT  XXV 

Testing  for  reserve  sugar  in  an  onion.  Boil  some  slices  of  onion  in  a  little 
water  and  filter  the  latter  through  a  paper  filter  to  remove  bits  of  the  bulb 
that  may  be  left  in  it.  Add  a  little  Fehling's  solution  to  the  liquid  thus 
obtained  and  heat  to  boiling.    Result  ?  i    What  is  proved  ? 

EXPERIMENT  XXVI 

Testing  an  onion  for  proteids.  Heat  a  rather  thick  slice  of  onion  in  a  por- 
celain evaporating  dish  v^ith  a  little  strong  nitric  acid  until  the  latter  just 
begins  to  boil. 2  Pour  off  the  excess  of  acid,  rinse  the  portion  of  onion  for 
a  moment  with  water,  and  add  enough  ammonia  to  cover  it.  Note  any 
color  changes.    What  is  proved  ? 


BUDS 

35.   Dissection  of  the  horse-chestnut  bud.^  *  *    Examine  one  of 

the  lateral  buds  on  a  twig  in  its  winter  or  early  spring  condition. 

A.  Make  a  sketch  of  the  external  appearance  of  the  bud  as 

seen  with  a  lens.    How  are  the  scales  arranged  ?    Notice  the 

sticky  coating  upon  them. 

1  The  mixture  usually  blackens  at  length,  probably  owing  to  the  presence  of 
sulphur  in  the  onion. 

2  Do  not  allow  the  acid  to  touch  the  hands  or  the  clothing. 

3  Buds  of  buckeye,  maple,  or  box  elder  will  answer,  but  not  as  well.    They  may 
be  forced  to  open  early  by  placing  twigs  in  water  in  a  warm  room  lor  several  weeks. 


DISSECTION    OF  A  WlNTKll   liUD 
B.    Remove  the  scales  in  pairs,  arranging  them  thus : 


49 


How  many  pairs  are  found  ? 

As  the  scales  are  removed  observe  whether  the  sticky  coat- 
ing is  thicker  on  the  outside  or  the  inside  of  each  scale,  and 
whether  it  is  equally  abundant  on  all  the  successive  pairs. 
What  do  you  suppose  to  be  the  probable  use  of  this  coating  ? 
Note  the  delicate  veining  of  some  of  the  scales  as  seen 
through  the  magnifying  glass.  What  does  this  mean  ? 
Inside  the  innermost  pair  are  found  two  forked,  woolly 
objects.  What  are  these?  Their  shape  could  be  more 
readily  observed  if  the  woolly  coating  were  removed.  Can 
you  suggest  a  use  for  the  woolly  coating  ? 
C.  Examine  a  terminal  bud  in  the  same  way  in  which  you 
have  just  studied  the  lateral  bud.  It  may  contain  parts 
not  found  in  tlie  other.  What  is  the  appearance  of  these 
parts  ?  What  do  they  represent  ?  If  there  is  any  doubt 
about  their  nature,  study  them  further  on  a  horse-chestnut 
tree  during  and  immediately  after  the  process  of  leahng 
out  in  spring,  or  let  the  twigs  remain  in  water  for  a  few 
weeks  until  the  buds  open. 


50     STRUCTURE  AND  PHYSIOLOGY  OF  SEED  PLANTS 

D.  For  comparison  study  at  least  one  of  the  following  kinds 
of  buds  in  their  winter  or  early  spring  condition :  hickory, 
butternut,  beech,  ash,  magnolia  (or  tulip  tree),  lilac,  balm  of 
Gilead,  cotton  wood,  cultivated  cherry.^ 

Eeference.    Ganong,  7. 

36.  Study  of  a  cabbage  (a  naked  bud).  Examine  and  sketch  a 
rather  small,  firm  cabbage,  preferably  a  red  one,  which  has  been 
split  lengthwise  through  the  center,  and  note  : 

A.  The  short,  thick,  conical  stem. 

B.  The  crowded  leaves  which  arise  from  the  stem,  the  lower 
and  outer  ones  largest  and  most  mature,  the  upper  and  inner- 
most ones  the  smallest  of  the  series. 

C.  The  axillary  buds,  found  in  the  angles  made  by  some  leaves 
with  the  stem. 

37.  Study  of  vernation.  Procure  a  considerable  number  of  buds  which  are 
just  about  to  burst,  and  others  which  have  begun  to  open.  Cut  each  across 
with  a  razor  or  very  sharp  scalpel ;  examine  first  with  a  magnifying  glass, 
and  then  with  the  lowest  power  of  the  microscope.  Make  a  careful  sketch 
of  one  section.  Pick  to  pieces  other  buds  of  the  same  kinds  under  the 
magnifying  glass,  and  report  upon  the  manner  in  which  the  leaves  are 
packed  away. 

Reference.    Kerner-Oliver,  2. 

38.  The  growing  apex  of  the  stem.  The  tip  of  the  stem  consists  of  tissue 
which  is  undergoing  (or  in  resting  buds  is  ready  to  undergo)  rapid  cell  divi- 
sion, thus  continuing  the  growth  of  the  stem.  The  structure  of  this  region 
in  dicotyledons  is  difficult  to  make  out  and  it  is  not  recommended  that 
beginners  should  undertake  to  study  it. 

Hippuris.^  Choose  a  stem  with  a  strong  terminal  bud,  and  trim  away 
from  near  the  tip  all  the  larger  leaves.  Cut  off  about  a  third  of  an  inch  of 
the  tip  of  the  stem,  hold  it  point  downward  between  the  thumb  and  fore- 
finger, and  try  to  get  a  smooth  longitudinal  section  through  the  axis  of  the 
bud.  If  the  latter  is  first  split  into  halves  and  then  successive  sections  are 
cut  from  each  half,  some  one  may  be  found  to  have  passed  exactly  through 

1  If  some  of  the  buds  are  studied  at  home,  pupils  will  have  a  better  chance  to 
examine  at  leisure  the  unfolding  process. 

2  If  Hippuris  is  not  available,  Myriophyllum,  which  grows  readily  in  aquaria 
the  year  round,  may  be  substituted. 


LEAVES  51 

the  middle  of  the'  bud.i  The  cell  contents  may,  in  great  part,  be  removed, 
and  the  sections  rendered  more  transparent  by  treating  them  for  some  time 
with  strong  potash  solution,  which  is  then  to  be  washed  out,  and  the  sections 
placed  in  concentrated  acetic  acid.  They  may  be  examined  in  acetic  acid  or 
in  a  solution  of  potassium  acetate. 

Examine  the  sections  with  a  power  of  200-300  diameters  and  make  out 
the  way  in  which  the  growing  apex  of  the  stem  is  capped  by  a  series  of 
layers  of  cells  as  follows  : 

A.  On  the  outside  a  single  layer,  the  dermatogen,  from  which  the  epi- 
dermis is  developed. 

B.  Beneath  this  the  periblem,  four  layers  of  cells  from  which  the  bark,  or 
cortex,  is  formed. 

C.  Within  the  layers  of  the  periblem,  the  pleronie,  out  of  which  tlie  axial 
fibro-vascular  bundle  of  the  stem  is  for  the  most  part  formed. 

Make  a  drawing  to  show  the  relations  of  all  the  parts  above  described,  and 
(lower  down  on  the  stem)  the  origins  of  the  leaves. 


LEAVES 

39.  The  elm  leaf.^  *  * 

A.  Sketch  the  leafy  twig  of  elm  that  is  supplied  to  you. 
Report  on  the  following  points  : 

1.  How  many  rows  of  leaves  ? 

2.  How  much  overlapping  of  leaves  when  the  twig  is  held 
with  the  upper  sides  of  the  leaves  tow^ard  you  ?  What 
would  be  the  advantages  or  disadvantages  of  much  over- 
lapping ?  Are  the  spaces  between  the  edges  of  the  leaves 
large  or  small  compared  with  the  leaves  themselves  ? 

B.  Pull  off  a  single  leaf  and  make  a  sketch  of  its  under  sur- 
face, about  natural  size.  Label  the  broad  part  the  blade,  the 
stalk  by  w^hich  it  is  attached  to  the  twig  leafstalk  or  petiole, 
the  a})pendages  at  its  base  stipules.  Study  the  outline  of  the 
leaf  and  answer  these  questions  (see  J*riticiples,  Appendix)  : 
1.  What  is  the  shape  of  the  leaf  as  a  whole  ? 

1  Unless  the  students  have  had  considerable  practice  in  making  sections  it  will 
be  better  to  purchase  slides  of  microtome  secti<iiis  of  some  growing  point. 

2  If  this  subject  is  taken  up  during  the  winter,  it  will  be  necessary  to  use  gera- 
nium or  other  leaves  from  the  florists  for  the  study  of  leaf  anatomy,  aud  potted 
geraniums,  begonias,  lilies,  etc.,  for  leaf  arrangement. 


52     STKUCTURE  AND  PHYSIOLOGY  OF   SEED  PLANTS 

2.  Is  the  leaf  bilaterally  symmet7ncal;  i.e.  is  there  a  middle 
line  running  through  it  lengthwise,  along  which  it  could 
be  so  folded  that  the  two  sides  would  nearly  coincide  ? 

3.  Is  the  leaf  dorsiventral;  i.e.,  has  it  distinct  upper  and 
under  surfaces  ? 

4.  Notice  that  the  leaf  is  traversed  lengthwise  by  a  strong 
midrib  and  that  many  so-called  veins  run  from  this  to 
the  margin.  Are  these  veins  parallel  ?  Hold  the  leaf  up 
towards  the  light  and  see  how  the  main  veins  are  con- 
nected by  smaller  veinlets.  Examine  with  your  glass  the 
leaf  as  held  to  the  light,  and  make  a  careful  sketch  of 
portions  of  one  or  two  veins  and  the  intersecting  veinlets. 
How  is  the  course  of  the  veins  shown  on  the  upper  sur- 
face of  the  leaf? 

5.  Examine  both  surfaces  of  the  leaf  with  the  glass  and  look 
for  hairs  distributed  on  the  surfaces.  Describe  the  man- 
ner in  which  the  hairs  are  arranged. 

40.  The  maple  leaf. 

A.  Sketch  the  leafy  twig. 

1.  How  are  the  leaves  arranged  ? 

2.  How  are  the  petioles  distorted  from  their  natural  posi- 
tions to  bring  the  proper  surface  of  the  leaf  upward  toward 
the  light  ? 

3.  Do  the  edges  of  these  leaves  show  larger  spaces  between 
them  than  the  elm  leaves  did  ;  i.e.  would  a  spray  of  maple 
intercept  the  sunlight  more  or  less  perfectly  than  a  spray 
of  elm  ?  Pull  off  a  single  leaf  and  sketch  its  lower  sur- 
face, about  natural  size. 

4.  Of  the  two  main  parts  (blade  and  petiole),  which  is  more 
developed  in  the  maple  than  in  the  elm  leaf  ? 

B.  Describe  : 

i.  The  shape  of  the  maple  leaf  as  a  whole.  To  settle  this, 
place  the  leaf  on  paper,  mark  the  positions  of  the  extreme 
points,  and  connect  these  by  a  smooth  line. 


LEAF    MOVKMKXrs   AND   LKillT  53 

2.  Its  outliRf  as  to  main  divisions.     Of  wliat  kind  and  how 
many  ? 

3.  The  detailed  outline  of  the  margin. 

Compare  the  mode  of  veining,  or  venation,  of  the  elm  and 
the  maple  leaf  by  making  a  diagram  of  each  (see  Principles, 
Chapter  X). 

The  leaves  of  ehn  and  of  maple  agree  in  being  netted  veined, 
i.e.  in  having  veinlets  that  join  each  other  at  many  angles,  so  as 
to  form  a  sort  of  delicate  lace  work. 

Such  a  leaf  as  that  of  the  elm  is  said  to  be  feather  veined,  or 
pinnately  veined.  The  maple  leaf,  or  any  leaf  with  closely  similar 
venation,  is  said  to  be  palmately  veined.  Describe  the  difference 
between  the  two  plans  of  venation. 


LEAF  ARRANGEMENT  FOR  EXPOSURE  TO  LIGHT 

AND  AIR;  HELIOTROPIC  MOVEMENTS  OF 

LEAVES  AND  SHOOTS 

EXPERIMENT  XXVII 

Is  the  nocturnal  position  due  to  removal  of  the  light  stimulus  or  to  other  causes  ? 

Remove  a  pot  containing  an  oxalis  or  a  clover  plant  from  a  sunny  window- 
to  a  dark  closet,  at  about  the  same  temperature,  and  note  at  intervals  of 
five  minutes  the  condition  of  its  leaves  for  half  an  hour  or  more. 

References.    Darwin  and  Acton,  11 ;   Pfeffer-Ewart,  31,  III ;    Detmer- 
Moor,  9. 

FA'PERIMENT  XXVIII 

Determination  of  the  values  of  illumination  to  produce  various  leaf  positions. ' 
Select  a  few  common  bean  plants  (Phaseolus)  growing  vigorously  in  a  sunny 
place,  or  a  locust  tree  {Robinia)  at  the  time  in  the  spring  when  its  leaves 
have  just  reached  their  full  size. 

A.  Note  and  sketch  the  positions  of  the  leaves  as  follows  : 

1.  After  dusk. 

2.  In  cloudy  daylight  or  near  dusk. 

3.  In  intense  sunlight,  near  noon. 

1  This  is  preferably  au  out-of-door  study. 


54     STRUCTURE  AND  PHYSIOLOGY   OF  SEED  PLANTS 

B.  Determine  the  relative  proportion  of  the  maximum  illumination  of 
sunlight  needed  to  bring  about  positions  1,  2,  and  3.  The  light  meas- 
urements are  to  be  made  by  means  of  ordinary  photographic  printing 
paper  ("solio"  paper  answers  well)  as  follows:  cut  the  paper  in  a 
very  dark  room  into  pieces  about  an  inch  square  and  at  once  put  them 
into  small  pasteboard  or  tin  boxes  and  shut  them  away  in  a  close  drawer 
or  a  windowless  closet.  All  the  paper  in  each  box  must  be  cut  from  the 
same  sheet  of  sensitive  paper.  One  square  of  paper  may  be  marked  with 
a  violet  aniline  pencil  and  then  exposed,  at  about  noon,  to  the  rays 
out  of  doors,  so  that  they  will  strike  it  vertically.  Note  exactly  with  a 
watch  in  how  many  seconds  the  pencil  mark  nearly  disappears.  The 
paper  should  then  be  at  once  shut  up  in  the  box  from  which  it  was 
taken.  This  darkened  square  of  paper  may  now  be  used  as  a  standard. 
If  it  darkened  in  30  seconds,  and  another  square  used  to  measure  illu- 
mination (1)  darkened  to  the  same  tint  in  2400  seconds,  then  illumina- 
tion (1)  was  gL  full  sunlight,  or  1.25  per  cent. 

RECORD 

Highest  illumination  for  position  1 

Average  illumination  for  position  2 

Least  illumination  for  position     3 

What  is  the  apparent  object  of  these  movements  ?  What  other  plants  have 
as  many  positions  as  the  bean  and  the  locust  ? 

Reference,  Pfeffer-Ewart,  31,  HI. 


EXPERIMENT  XXIX 

Can  growing  leaves  adapt  their  positions  to  new  light  relations  ?  *  "* 

Select  a  young,  leafy,  vertical  branch  of  maple  growing  out  of 
doors,  or  a  vigorous  young  sunflower  (Helianthus)  plant  growing 
out  of  doors  or  under  nearly  vertical  light.^  Bend  the  shoot  into 
a  horizontal  position  and  note  whether  the  leaves  adapt  them- 
selves to  their  new  relations.  If  there  is  any  adaptation,  describe 
exactly  the  leaf  movements  by  which  it  is  brought  about. 

Reference.    Pfeffer-Ewart,  31,  III. 

1  Less  satisfactory  studies  can  be  made  of  geraniums,  begonias,  or  other  plants 
grown  in  the  window  and  turned  at  intervals  of  several  weeks. 


MINUTE  STRUCTURE  OF  LEAVES  55 

EXPERIMENT  XXX 

How  do  young  shoots  of  English  ivy  bend  with  reference  to  light  ?  Place  a 
thrifty  potted  plant  of  English  ivy  before  a  small  window,  e.g.  an  ordinary 
cellar  window,  or  in  a  large  covered  box,  painted  dull  black  within  and 
open  only  on  the  side  toward  a  south  window.  After  some  days  note  the 
position  of  the  tips  of  the  shoots.  Explain  the  use  to  the  plant  of  their 
movements. 

Reference.    Detmer-Moor,  9. 

41.  Sun  leaves  and  shade  leaves. ^  Select  for  study  some  species  of  shrub 
or  tree  which  furnishes  a  dense  shade.  Deciduous  species  will  answer,  but 
broad-leafed  evergreens,  like  hollies,  some  rhododendrons,  or  live  oaks  are 
still  better.  Why  ?  Gather  some  of  the  outer  leaves  and  some  of  the  inner- 
most ones  from  the  same  tree.  Measure  the  per  cent  of  total  illumination 
received  by  the  innermost  leaves,  as  described  in  Exp.  XXVIII.  Make  a 
detailed  comparison  of  the  two  kinds  of  leaves  (those  grown  in  sun  and  in 
shade)  as  follows  : 

A.  Comparison  of  average  areas  (see  Exp.  XXXVIII). 

B.  Comparison  of  hairiness  or  scaliness  of  the  under  surfaces. 

C.  Comparison  of  thickness  of  leaves.  Use  a  power  of  25-50  diameters 
and  a  micrometer  eyepiece,  if  one  is  available. 

D.  Comparison  of  details  of  structure  of  cross  sections  (see  Sees.  42,  43). 
Explain  as  fully  as  possible  all  the  differences  noted  in  comparisons 
A-D  above. 

Reference.    Clements,  59. 

MINUTE  STRUCTUEE  OF  LEAVES;  FUNCTIONS 
OF  LEAVES 

42.  Minute  structure  of  lily  leaf.^  *  * 

A.  The  student  should  lirst  examine  with  m.p.  a  cross  section 
of  the  leaf.    This  will  show  : 

1.  Tlie  upper  epidermis  of  the  leaf,  a  thin,  nearly  transpar- 
ent membrane. 

2.  The  intermediate  tissues. 

3.  The  lower  ei)idermis. 

1  A  simpler  study  may  be  mado  by  comparing  the  illuminations  and  structures 
of  characteristic  sun  plants  and  sIkkU-  plants,  for  instance  Portuhica,  Spduin,  etc., 
with  Atisu-.ma,  Aralia,  Cilntonid,  Tri/liiini,  etc..  cacli  tjrown  in  its  natural  liabitat. 

2  Any  kind  of  lily  will  answer.  Otlier  Icavss  are  equally  j^'ood  but  manv  of 
them  are  not  obtainable  at  all  seasons.    Some  excellent  kinds  are  Fuchnia,  En;:lish 


56      STRUCTURE   AND   PHYSIOLOGY   OF   SEED  PLANTS 

In  ordpr  to  ascertain  the  relations  of  the  parts,  and  to  get 
their  names,  consult  Principles,  Fig.  112.  l^our  section  is  by  no 
means  exactly  like  the  figure ;  sketch  it.  Label  properly  all  the 
parts  shown  in  your  sketch. 

Are  any  differences  noticeable  between  the  upper  and  the  lower 
epidermis  ?  Between  the  layers  of  cells  immediately  adjacent  to 
each  ?  Test  some  sections  with  phloroglucin  (Sec.  12,  D). 

B.  Examine  with  a  power  of  200  or  more  diameters  the  outer 
surface  of  a  piece  of  epidermis  from  the  lower  side  of  the 

•  leaf.^    Sketch  carefully,  comparing  your  sketch  with  Prin- 
ciples, Fig.  113,  and  labeling  it  to  agree  with  that  figure. 

C.  Examine  another  piece  from  the  upper  surface ;  sketch  it. 
How  does  the  number  of  stomata  in  the  two  cases  compare  ? 

E-EFEREXCE.    Strasburger-Hillhouse,  6. 

43.  Study  of  the  leaf  of  "  rubber  plant  "  (Ficus  elastica)*  * 

A.  Make  preparations  of  the  leaf  of  the  so-called  rubber  plant 

as  already  described  for  the  lily  leaf.    Study  and  sketch  them 

and  then  compare  the  two  types  of  leaf : 

1.  As  regards  thickness  of  epidermis. 

2.  As  regards  number  of  layers  of  cells  in  the  epidermis. 

3.  As  regards  development  of  the  palisade  layers. 

4.  As  regards  amount  of  fibro-vascular  material  (veins). 

5.  As  regards  freedom  of  exposure  of  the  stomata  openings 
to  the  air. 

ivy  (Heclera),  willow,  maple,  poplar  (any  species,  as  cottonwood,  aspen,  etc.),  the 
thicker-leaved  species  of  aster,  apple,  pear,  plum,  quince,  beet.  Thin  sections 
may  be  cut  free-hand,  especially  if  the  leaf  is  doubled  together  several  times  or 
held  between  two  bits  of  elder  pith.  If  only  a  part  of  the  section  is  very  thin,  it 
will  answer  almost  as  well  as  if  it  were  equally  thin  throughout.  The  sections 
may  be  made  much  more  transparent  if  they  are  soaked  in  potash  solution  until 
most  of  the  green  color  disappears,  and  then  treated  with  acetic  acid.  Both 
these  sections  and  those  in  their  natural  condition  should  be  examined.  Some 
sections  in  their  natural  condition  should  be  treated  with  phloroglucin. 

1  The  epidermis  may  be  started  with  a  sharp  scalpel  and  then  peeled  off  with 
small  forceps  and  movinted  in  water  for  microscopical  examination.  The  epidermis 
of  Ficus  leaf  (Sec.  43)  will  need  to  be  pared  off  with  a  very  sharp  razor  held  par- 
allel to  the  leaf  surface.  The  stomata  may  be  counted  by  use  of  an  eyepiece 
micrometer  ruled  in  squares.  Find  how  many  divisions  of  the  stage  micrometer 
equal  one  side  of  this  square;  then  substitute  a  bit  of  epidermis  for  the  stage 
micrometer,  and  count  the  number  of  stomata  in  an  eyepiece  square.  Calculate 
the  number  of  stomata  in  a  leaf  of  the  kind  examined;  also,  if  possible,  the 
number  for  the  entire  plant. 


riioiosVM  iiKsis  67 

B.  Let  an  entire  leaf  of  each  kind  remain  for  some  hours  in  a 
warm,  sunny  place  and  notice  the  comparative  amount  of 
wilting  in  both  cases.    Explain. 

Refkhkncks.  Kerner-Oliver,  2;  Haberlandt,  33;  Schimper- 
Fisher^,  56;  Warming-Graebner,  57. 

EXPERIMENT  XXXI 

Oxygen  making  in  sunlight.  *  *  Place  a  green  aquatic  plant  in 
a  glass  jar  full  of  water,  at  about  70°  F.  (21°  C),  in  front  of  a 
sunny  window.^  Note  the  formation  of  oxygen  bubbles  looking 
silvery  by  reflected  light.^  Remove  to  a  dark  closet  and  after 
fifteen  minutes  examine  by  lamplight,  to  see  whether  the  rise  of 
bubbles  still  continues. 

This  gas  may  be  shown  to  be  oxygen  by  collecting  some  of  it 
in  a  small  inverted  test  tube  filled  with  water  and  thrusting 
into  it  the  glowing  coal  of  a  match  just  blown  out.  It  is  not, 
however,  always  very  easy  to  do  this  satisfactorily. 

Repeat  the  experiment,  using  water  which  has  been  well 
boiled  and  then  quickly  cooled  in  a  tightly  covered  vessel. 
Boiling  removes  all  the  dissolved  gases  from  water  (including 
much  carbon  dioxide),  and  they  are  not  redissolved  in  any 
considerable  quantity  for  many  hours. 

References.    Detmer-Moor,  9  ;  Darwin  and  Acton,  11. 

EXPERIMENT   XXXII 

Occurrence  of  starch  in  nasturtium  leaves.*  *  Toward  the  close 
of  a  very  sunny  day  collect  some  bean  leaves  or  leaves  of  nastur- 
tium (TrojHvolum).  Boil  these  in  water  for  a  few  minutes,  to  kill 
the  protoplasmic  contents  of  the  cells  and  to  soften  and  swell 
the  starch  grains.  Soak  the  leaves,  after  boiling,  in  strong,  hot 
alcohol  for  half  an  hour,  to  dissolve  out  the  chlorophyll,  which 

1  FJodea,  yfyriophylliDn,  ('hriisnspjcii'mm,  Potainogeton,  any  of  the  preen 
aquatic  tlowcriu";  plants,  the  a(niatic  moss,  Fontinalis,  or  even  the  common  pond 
scum,  Spiroffyra,  will  (h)  for  this  experiment. 

2  Some  of  the  earlier  bnhhles  may  contain  a  good  deal  of  air  which  was 
dissolved  in  the  water  and  set  free  as  it  grows  warm,  but  the  later  bubbles  will 
be  fairly  pure  oxygen. 


58     STKUCTUJIE  AND   J'IIYSlOLO(;V   OF   SEED  PLANTS 

might  obscure  the  starch  test.  Heat  the  alcohol  in  a  water  bath 
away  from  any  flame.  Place  the  leaves  for  ten  or  fifteen  minutes 
in  a  solution  of  iodine,  rinse  off  with  water,  put  in  a  white  plate 
or  saucer,  and  note  what  portions  of  the  leaf,  if  any,  show  the 
presence  of  starch. 

References.    Detmer-Moor,    9  ;     Ganong,    10 ; .   Darwin    and 
Acton,  11  ;  Pfeffer-Ewart,  31,  I. 


EXPERIMENT  XXXTTI 

Consumption    of    starch    in    nasturtium   (Tropaeolum)    leaves.*  * 

Select  some  healthy  leaves  of   Trojxvoluni  on  a  plant  growing 
vigorously  indoors,  or,  still  better,  in  the  open  air.     Shut  off  the 

sunlight  from  parts  of  the  selected 
leaves  (which  are  to  be  left  on  the 
plant  and  as  little  injured  as  possible) 
by  pinning  circular  disks  of  cork 
loosely  on  opposite  sides  of  the  leaf, 
as  shown  in  Fig.  3.  On  the  afternoon 
of  the  next  day  remove  from  the  plant 
these  leaves  and  (for  control  purposes) 
some  others  to  which  no  cork  disks 
were  attached.  Treat  all  as  described 
in  the  preceding  experiment,  taking 
especial  pains  to  get  rid  of  the  chlorophyll  by  changing  the 
alcohol  as  many  times  as  may  be  necessary.  AVhat  does  this 
experiment  show  in  regard  to  the  consumption  of  starch  in  the 
leaf  ?    What  has  caused  its  disappearance  ?  ^ 

It  may  be  fairly  taken  for  granted  that  if  the  leaf  contained  any 
starch  when  the  corks  were  pinned  onto  it,  all  parts  of  it  were 
somewhat  equally  full  of  starch.  If  the  experiment  results  in 
showing 'absence  of  starch  in  the  part  deprived  of  light  by  the 
cork,  it  may  be  thought  that   starch  manufacture  was   stopped 

1  Or  put  a  plant  with  starch  in  the  leaves  in  a  moist  chamber  without  light 
for  a  day  or  two,  with  cut-ofp  leaves  beside  it.  Then  test  the  attached  leaves  and 
the  cut-off  ones  for  starch.    Ex])lain  results. 


yj.  Leaf  of  Tropceolum 
partly  covered  with  disks  of 
cork  and  exposed  to  sunlight 


PHOTOSYNTHESIS  59 

in  that  portion  partly  because,  of  lack  of  li^bt.  and  partly  l-)ecaus« 
the  sup})ly  of  air  (and  t.licrcforc  of  carhoii  dioxide)  was  very 
scanty  under  the  cork.  The  truth  of  the  supposition  that  lack  of 
carbon  dioxide  was  responsible  for  the  failure  to  make  starch 
may  be  tested  by  boring  a  large  hole  with  a  cork  borer  through 
each  cork  before  fastening  it  in  place  on  the  leaf,  and  cementing 
over  the  hole  a  thin  cover  glass.  Then  some  of  the  parts  of  the 
leaf  covered  by  the  cork  are  lighted  while  others  are  not,  and  if 
the  lighted  parts  show  starch,  it  was  lack  of  light  only  that 
prevented  its  formation  in  the  shaded  parts. 

Keferences.     (See  Experiment  XXXll.) 

EXPKRnn<:xT  xxxiv 

Can  starch  making  go  on  when  the  stomata  are  shut  off  from  all 
air  supply?  Select  a  thrifty  potted  plant  of  some  species  which 
has  thin  leaves,  with  stomata  only  on  the  under  surface  (e.g.  prim- 
rose, begonia).  Put  the  plant  in  an  absolutely  dark  place  for 
twenty -four  hours,  and  then  coat  half  of  the  under  surface  of  one 
or  more  leaves  with  vaseline  and  expose  the  plant  for  a  day  to 
bright  sunlight.  Wipe  off  most  of  the  vaseline  with  cotton  wool 
and  remove  the  rest  by  washing,  with  a  swab  or  soft  brush,  in 
several  successive  quantities  of  benzine.^  Then  boil,  treat  with 
alcohol,  and  test  for  starch  as  directed  in  Exp.  XXXII.  Explain 
the  result. 

Kkkekexce.     Ganong,  10. 

KXl'ERTMENT   XXXV 

Can  squash  seedlings  make  chlorophyll  in  the  dark  ?  *  *  l*lant 
some  squash  seeds  in  sawdust  or  sand,  and  keep  part  of  them  in 
a  good  light,  while  others  are  kept  in  total  darkness  at  about  the 
same  temperature.  When  the  plumules  of  those  in  the  light  are 
developed  into  half-grown  leaves,  skc^teh  both  lots  of  seedlings 

1  Do  not  iittenipt  this  in  tlie  same  room  with  a  tiame,  or  a  li^htctl  lamj)  or 
gas  jet. 


00     STRUCTUrvK  AND   PIIYSTOl.OGY  OF   SEED  PLANTS 

and  describe  the  main  differences  in  color,  height,  and  thickness 
of  hypocotyl,  and  in  the  development  of  the  cotyledons  of  those 
grown  in  darkness  and  in  the  light. 

What  is  the  conclusion  in  regard  to  power  to  make  chlorophyll  ? 

Leave  both  lots  in  sunlight  for  a  day  and  test  some  cotyle- 
dons of  each  set  for  starch.  Leave  both  sets  in  sunlight  for 
several  days  more  and  note  any  changes  in  the  appearance  of 
those  which  were  started  in  darkness.  Test  the  latter  again  for 
starch.    Conclusions  ? 

Reference.    Pfeft'er-Ewart,  31,  II. 

EXPERIMENT   XXXVI 

Do  leaves  give  off  water  ?  If  so,  from  which  surface  is  it  given  off 
more  abundantly?  *  *  Fasten  two  small  watch  glasses,  one  on  each 
side  of  a  leaf  of  a  plant  growing  vigorously  in  a  pot  or  out  of  doors. 


Fig.  4.    Watch  glasses  fastened  on  a  leaf  of  Chinese  primrose 

Hydrangea,^  primrose,  or  cineraria  ^  are  good  plants  for  the  pur- 
pose, although  many  others  will  answer.  The  watch  glasses  may 
be  held  in  place  by  a  spring  clip,  as  shown  in  Fig.  4.  Seal  the 
margin  of  each  glass  all  the  way  around  by  means  of  vaseline  or 
barely  melted  grafting  wax.  Leave  the  plant  for  half  an  hour  or 
more  in  a  sunny  place,  and  then  look  for  drops  of  water  inside 
1  H.  Hortensia.  2  Senecio  cruentus. 


TRANSPIRATION  61 

of  each  watch  glass.  If  none  are  visible,  carefully  cut  off  the  leaf 
and  place  it  for  a  few  minutes  in  a  box  with  a  piece  of  ice  or 
put  it  out  of  doors  in  a  cold  place.  Report  the  results.  Examine 
the  upper  and  lower  epidermis  with  the  microscope  and  explain 
the  results  noted. 

Reference.    Osterhout,  13. 

EXPERIMENT  XXXVII  ^ 

Through  which  side  of  a  leaf  of  Ficus  elastica  does  transpiration  occur  ?   The 

student  may  already  have  found  (Sec.  43)  that  there  are  no  stomata  on 
the  upper  surface  of  the  Ficus  leaf  which  he  studied,  i  That  fact  makes  this 
leaf  an  excellent  one  for  the  study  of  the  relation  of  stomata  to  transpiration. 

Take  two  large,  sound  Ficus  leaves,  cut  off  pretty  close  to  the  stem  of  the 
plant.  Slip  over  the  cut  end  of  the  petiole  of  each  leaf  a  piece  of  small 
rubber  tubing,  wire  this  on,  leaving  about  half  of  it  free,  and  then  double  the 
free  end  over  and  wire  tightly,  so  as  to  make  the  covering  moisture  proof. 
"Warm  some  vaseline  or  grafting  wax  until  it  is  almost  liquid,  and  spread  a 
thin  layer  of  it  smoothly  over  the  upper  surface  of  one  leaf  and  the  lower 
surface  of  the  other.  Hang  both  up  in  a  sunny  place  in  the  laboratory  and 
watch  them  for  a  month  or  more. 

What  difference  in  the  appearance  of  the  two  leaves  becomes  evident  ? 
What  does  the  experiment  prove  '? 

Reference.     Darwin  and  Acton.  11. 


EXPERIMENT  XXXVIII 

Amount  of  water  lost  by  transpiration.  *  *  Procure  a  thrifty  hydrangea  ^  and 
a  small  plant  of  Ficus  elastica,'^  each  growing  in  a  small  flowerpot,  and  with 
the  number  of  scjuare  inches  of  leaf  surface  in  the  two  plants  not  too  widely 
different.  Calculate  the  area  of  the  leaf  surface  for  each  plant  by  dividing 
the  surface  of  a  piece  of  tracing  cloth  into  a  series  of  squares  one  half  inch 
on  a  side,  holding  an  average  leaf  of  each  plant  against  this  and  counting 
the  munber  of  squares  and  parts  of  squares  covered  by  the  leaf.  This  area, 
nniltiplied  by  the  number  of  leaves  for  each  plant,  will  give  approxijuately 
the  total  evaporating  surface  for  each.* 

1  Tins  is  also  true  of  many  other  leaves,  as  tlidse  of  the  oleander,  the  lilac,  ami 
most  lu-ijonias.  ami  any  of  them  may  be  used  for  the  experiment. 

-  'IMii'  common  species  of  the  lireenhoiise.  //i/ilntiif/iit  Uortfiis'uc. 

•'  (ommnnly  known  as  India-nihher  i»lant. 

*  The  quickest  and  most  accurate  method  of  procedure  is  to  defer  calculating 
the  leaf  aica  until  the  i-onclusion  of  the  experiment,  and  then  to  cut  off  all  the 


62     STKUCri'KK   AXi)   TJIYSlOLOGY   OF   SEED   PLANTS 


Transfer  each  plant  to  a  glass  battery  jar  of  suitable  size.  Cover  the  jar 
with  a  piece  of  thin  sheet  lead,  slit  to  admit  the  stem  of  the  plant,  invert 
the  jar,  and  seal  the  lead  to  the  glass  with  a  hot  mixture  of  beeswax  and 
rosin.  Seal  up  the  slit  and  the  opening  about  the  stem  with  grafting  wax.i 
A  thistle  tube,  such  as  is  used  by  chemists,  is  also  to  be  inserted,  as  shown 

in  Fig.  o.  The  mouth  of  this  may  be 
kept  corked  when  the  tube  is  not  in 
use  for  watering. 

Water  each  plant  moderately  and 
weigh  the  plants  separately  on  a 
balance  that  is  sensitive  to  one-fifth 
gram.  Record  the  weights,  allow  the 
plants  to  stand  in  a  sunny,  'warm 
room  for  twenty-four  hours,  and 
reweigh. 

Add  to  each  plant  just  the  amount 
of  water  which  is  lost,^  and  continue 
the  experiment  in  the  same  manner 
for  several  days,  so  as  to  ascertain,  if 
possible,  the  effect  upon  transpiration 
of  varying  amounts  of  water  in  the 
atmosphere. 

Calculate  the  average  loss  per  100 
square  inches  of  leaf  surface  for  each 
plant  throughout  the  whole  course  of 
the  experiment.  Divide  the  greater  loss  by  the  lesser  to  find  the  ratio.  Find 
the  ratio  of  each  plant's  greatest  loss  per  day  to  its  least  loss  per  day,  and 
by  comparing  these  ratios  decide  which  transpires  more  regularly. 

Try  the  effect  of  supplying  very  little  water  to  each,  so  that  the  hydran- 
gea will  begin  to  droop,  and  see  whether  this  changes  the  relative  amount  of 
transpiration  for  the  two  plants.  Vary  the  conditions  of  the  experiment  for 
a  day  or  two  as  regards  temperature,  and  again  for  a  day  or  two  as  regards 
light,  and  note  the  effect  upon  the  amount  of  transpiration. 

The  structure  of  the  Ficiis  (India-rubber  plant)  leaf  has  already  been 
studied.  That  of  the  hydrangea  is  looser  in  texture  and  more  like  the  leaf 
of  the  lily. 

leaves,  make  blue  prints  of  them,  cut  these  out,  and  weigh  them.  The  total  area 
may  easily  be  calculated  by  comparison  of  the  weight  obtained  with  that  of  a 
known  area  of  the  paper  used. 

1  It  will  be  much  more  convenient  to  tie  tlie  liydrangea,  if  one  has  been  chosen 
that  has  but  a  single  main  stem.  Instead  of  the  hydrangea  the  common  (dneraria, 
Stnecio  eruentii.s,  or  a  small  suntlower  plant  does  very  well. 

2  The  addition  of  known  amounts  of  water  may  be  "made  most  conveniently  by 
measuring  in  a  cylindrical  graduate. 


hydrangea    potted    in    a 
battery  jar  for  Exp.  XXXVIII 


kim:  of  w  a  tkk  63 

WliiU    li;;ht  docs   the   sLriicLuiv    thr.iw   mi    (he    results  of    the   preceding 

('XpClillH'Ilt   '.' 

l\i:ri:iii:NCKs.     Detiuer-Moor ,'.»  ;  (laiKHiir,  1<*. 


EXPERIMKX'I"   XXXIX 

Passage  of  water  from  stem  to  leaf.  I'lacc  m  fnslily  cut  Icafv 
shoot  of  some  plant  with  large,  thin  leaves,  sudi  as  Uijili-aivini 
Ilortensid,  in  eosin  solution  for  a  few  minutes.  As  soon  as  tin* 
leaves  show  a  decided  reddening  pull  soiiu^  of  them  off  and 
sketch  the  red  stains  on  the  scars  thus  made.  What  does  tliis 
show  ? 

EXl'KKLMKXT   XE 

Rise  of  water  in  leaves.*  *  Tut  the  freshly  cut  ends  of  tlu' 
petioles  of  several  tliin  leaves  of  different  kinds  into  small  glasses, 
each  containing  eosin  solution  to  the  depth  of  one  quarter  inch  oi- 
more.  Allow  them  to  stand  for  half  an  hour,  and  examine  them 
by  holding  up  to  the  light  and  looking  through  tliem  to  see  into 
what  parts  the  eosin  solution  has  risen.  Allow  some  of  the  leaves 
to  remain  as  much  as  twelve  hours,  and  examine  them  again. 
The  red-stained  portions  of  the  leaf  mark  the  lines  along  which, 
under  natural  conditions,  water  rises  into  it.  Cut  across  (near  the 
petiole  or  midrib  ends)  all  the  principal  veins  of  some  kind  of 
large,  thin  leaf.  Then  cut  off  the  petiole  and  at  once  stand  the 
cut  end,  to  which  the  Idade  is  attached,  in  eosin  solution.  Ivcpeat 
with  another  leaf  and  stand  in  watei-.    AVhat  do  the  results  teacli".' 

KXI'KKIMKN  r   XLI 

Does  the  leaf  vary  in  its  starch  contents  at  different  seasons?  Collect  in 
early  suinmer,  at  the  close  of  a  sunny  day,  some  leaves  of  different  kinds  of 
trees  and  shrubs  and  preserve  them  in  alcohol.  Collect  other  leaves  of 
the  species  as  they  are  befjinninj;  to  droji  from  the  trees  in  autumn  and  pn*- 
.serve  them  in  the  same  way.  Test  some  of  cuch  lot  for  starch,  :us  de.scribtMl 
in  K.\p.  XXXII. 

What  does  the  result  indicate  ? 


64     STRUCTURE  AND  PHYSIOLOGY   OF  SEED  PLANTS 

THE  FLOWER  OF  THE  HIGHER  SEED  PLANTS 

44.  The  flower  of  the  Trillium.  ^  *  * 

A.  Cut  off  the  flower  stalk  rather  close  to  the  flower  ;  stand  the 
latter,  face  down,  on  the  table,  and  draw  the  parts  then 
shown.  Label  the  green  leaf -like  parts  sepals,  and  the  white 
parts,  which  alternate  with  these,  petals. 

B.  Turn  the  flower  face  up  and  make  another  sketch,  label- 
ing the  parts  as  before,  together  with  the  enlarged  yellow  ex- 
tremities, or  anthers,  of  the  stalked  organs  called  stamens. 

C.  Note  and  describe  the  way  in  which  the  petals  alternate 
with  the  sepals.  Observe  the  arrangement  of  the  edges  of 
the  petals  toward  the  base,  —  how  many  with  both  edges 
outside  the  others,  how  many  with  both  edges  inside,  how 
many  with  one  edge  in  and  one  out. 

Note  the  veining  of  both  sepals  and  petals,  observing  in 
which  set  they  are  more  distinct.  ^ 

D.  Pull  off  a  sepal  and  make  a  sketch  of  it,  natural  size ;  then 
remove  a  petal,  flatten  it  out,  and  sketch  it,  natural  size. 

E.  Observe  that  the  flower  stalk  is  enlarged  slightly  at  the 
upper  end  into  a  rounded  portion,  the  receptacle,  on  which 
all  the  parts  of  the  flower  rest. 

F.  Note  how  the  six  stamens  arise  from  the  receptacle, 
and  their  relations  to  the  origins  of  the  petals.  Remove  the 
remaining  petals  (cutting  them  off  near  the  bottom  with  a 

1  Only  one  flower  need  be  studied  to  give  an  idea  of  the  floral  organs  ordinarily 
found.    More  advanced  studies  are  suggested  at  the  end  of  Part  III. 

If  none  of  the  three  flowers  here  described  can  be  had,  the  instructor  can 
readily  frame  a  set  of  directions  for  the  examination  of  some  other  form.  Among 
the  simplest  types  which  can  readily  be  grown  in  the  greenhouse  for  class  study 
are  Sedum  acre  and  Crassula  quadrifida.  Matthiola  is  not  quite  so  simple,  but 
the  single-flowered  varieties  answer  very  well.  Scilla  sibirica  is  often  available. 
Another  convenient  greenhouse  flower  is  the  Roman  hyacinth. 

2  In  flowers  with  delicate  white  petals  the  distribution  of  the  fibro-vascular 
bundles  can  usually  be  readily  shown  by  standing  the  freshly  cut  end  of  the 
flower  stalk  in  eosin  for  a  short  time,  until  colored  veins  begin  to  appear  in  the 
petals.  The  experiment  succeeds  readily  with  apple,  cherry,  or  plum  blossoms;  with 
white  gillyflower  the  coloration  is  very  prompt.  Lily  of  the  valley  is  perhaps  as 
interesting  a  flower  as  any  on  which  to  try  the  experiment,  since  the  well-defined 
stained  stripes  are  separated  by  portions  quite  free  from  stain,  and  the  pistils 
are  also  colored. 


FLOWKK    OF    rillLLIUM  65 

knife),   and   sketch  the  stamens,  together  with   the   other 
structure,  the  pistil,  which  stands  in  the  center. 

Cut  oft"  one  stamen,  and  sketch  it  as  seen  through  the  lens. 
Notice  that  it  consists  of  a  greenish  stalk,  the  f  lament,  and 
a  broader  portion,  the  anther.  The  latter  is  easily  seen  to 
contain  a  prolongation  of  the  green  filamc^nt,  nearly  sur- 
rounded by  a  yellow  substance.  In  the  bud  it  will  be  found 
that  the  anther  consists  of  four  long  pouches,  or  j/olleri  <limii- 
bers,  which  are  attached  by  their  whole  length  to  the  fila- 
ment. When  the  flower  is  fairly  open  the  pollen  chambers 
of  each  pair  have  already  split  down  their  margins,  thus 
appearing  as  one  on  each  side,  and  are  discharging  a  yellow, 
somewhat  sticky  powder,  the  2^ollen. 

Examine  one  of  the  anthers  wdth  a  lens  and  sketch  it. 
Cut  thin  cross  sections  of  an  immature  anther  and  draw 
under  l.p.,  showing  the  pollen  chambers. 

G.  Cut  away  all  the  stamens  and  sketch  the  pistil.  It  consists  of  a 
stout  lower  portion,  the  ovule  case,  or  ovary,  which  is  six-ridged 
or  angled,  and  which  bears  at  its  summit  three  slender  stigmas. 
In  another  flower,  which  has  begun  to  wither  (and  in  which 
the  ovary  is  larger  than  in  a  newly  opened  flower),  cut  the 
ovary  across  about  the  middle,  and  with  the  lens  determine 
the  number  of  chambers,  or  loonies,  which  it  contains.  Exam- 
ine the  cross  section  with  the  lens;  sketch  it,  and  note  par- 
ticularly the  appearance  and  mode  of  attachment  of  the 
undeveloped  seeds,  or  ovules,  wdth  which  it  is  filled.  Make  a 
vertical  section  of  another  rather  mature  ovary,  and  examine 
this  in  the  same  way. 

H.  Using  a  fresh  flower,  construct  a  diagram  to  show  the  rela- 
tion of  the  parts  on  an  imaginary  cross  section.^  Construct 
a  diagram  of  a  longitudinal  section  of  the  flower,  showing 
the  contents  of  the  ovary. 

1  It  is  iiiipDitjint  to  notice  that  such  a  diaj^raiM  is  not  a  picture  of  the  sectiou 
actually  produced  liy  cuttiuj;  through  the  dower  crosswise  at  any  one  level,  but 
that  it  is  rather  a  projcvdo/i  of  the  sections  ihroujjh  the  most  typical  part  ol  eacii 
of  the  tioral  organs  (see  rrinciples,  Fig.  LIS). 


66     STRUCTURE   AXJ)   rilYSIOLOGY   OF  SEED   PLANTS 

Make  a  tabular  list  of  the  parts  of  the  flower,  beginning 
with  the  sepals,  giving  the  order  of  parts  and  the  number  in 
each  set. 

45.  The  flower  of  the  tulip. ^ 

A.  Make  a  sketch  of  a  side  view  of  the  well-opened  flower  as  it  appears 
when  standing  in  sunlight.  Observe  that  there  is  a  set  of  outer  flower 
leaves  and  a  set  of  inner  ones.'^  Label  the  outer  set  sepals  and  the  inner 
set  petals.  In  most  flowers  the  parts  of  the  outer  set  are  greenish,  and 
those  of  the  inner  set  of  some  other  color.  It  is  often  convenient  to 
use  the  name  perianth  (meaning  around  the  flower)  for  the  two  sets 
taken  together.  Note  the  white  waxy  bloom  on  the  exterior  surface 
of  the  outer  segments  of  the  perianth.  What  is  the  use  of  this  ?  Observe 
the  manner  in  which  the  inner  segments  of  the  perianth  arise  from  the 
top  of  the  flower  stalk  and  their  relation  to  the  points  of  attachment  of 
the  outer  segments.  In  a  flower  not  too  widely  opened  note  the  relative 
position  of  the  inner  segments  of  the  perianth,  how  many  wholly  outside 
the  other  two,  how  many  wholly  inside,  how  many  with  one  edge  in 
and  one  edge  out. 

B.  Remove  one  of  the  sepals  by  cutting  it  off  close  to  its  attachment  to 
the  peduncle,  and  examine  the  veining  by  holding  it  up  in  a  strong 
light  and  looking  through  it.  Make  a  sketch  to  show  the  general  out- 
line and  the  shape  of  the  tip. 

C.  Examine  a  petal  in  the  same  way,  and  sketch  it. 

D.  Cut  off  the  remaining  portions  of  the  perianth,  leaving  about  a  quarter 
of  an  inch  at  the  base  of  each  segment.  Sketch  the  upright,  triangular, 
pillar-like  structu.re  in  the  center, — label  it  pistil;  sketch  the  organs 
which  spring  from  around  its  base,  and  label  these  stamens. 

Note  the  fact  that  each  stamen  arises  from  a  point  just  above  and 
within  the  base  of  a  segment  of  the  perianth.  Each  stamen  consists  of 
a  somewhat  conical  or  awl-shaped  portion  below,  the  filament,  sur- 
mounted by  an  ovate-linear  portion,  the  anther. 

E.  Sketch  one  of  the  stamens  about  twice  natural  size  and  label  it  x  2. 
Is  the  attachment  of  the  anther  to  the  filament  such  as  to  admit  of 
any  nodding  or  twisting  movement  of  the  former  ?  In  a  young  flower 
note  the  tubular  pouches,  or  pollen  chambers,  of  which  the  anther  is 
composed,  and  the  slits  by  which  these  open.  Observe  the  dark-colored 
pollen  which  escapes  from  the  anther  cells  and  adheres  to  paper  or  to 
the  fingers.  Examine  a  newly  opened  anther  with  the  lens  and  sketch 
it.  Cut  thin  cross  sections  of  an  unopened  anther  and  examine  with  l.p. 
Note  that  there  are  four  pollen  chambers,  two  on  each  side. 

1  Tulipa  Uttsiiarlaiia.       ^  Best  seen  iu  a  flower  which  is  just  opening. 


FI.OWKK   ()!•     lU    riKKCl  1'  67 

F.  Cut  away  all  the  .staincns  and  note  the  two  portions  of  the  pistil, — 
the  ovule  case,  or  ovary,  below,  and  above  three  rou^diened,  S(;n)ll-like 
lobes  of  the  stigma.  Make  a  sketch  of  these  parts  about  twice  natural 
size,  and  label  them  x  2,  Touch  a  small  camePs-hair  brush  to  one  of 
the  anthers  and  then  transfer  the  pollen  thus  removed  to  the  stigma. 
This  operation  is  merely  an  imitation  of  the  work  done  by  insects  which 
visit  the  flowers  out  of  doors.  Does  the  pollen  cling  rea<lily  to  the 
rough  stigmatic  surface  ?  Examine  this  adhering  pollen  under  l.p.  and 
sketch  a  few  grains  of  it,  together  with  the  bit  of  the  stigma  to  which 
it  clings.  Make  a  cross  section  of  the  ovary  about  midway  of  its 
length,  and  sketch  the  section  as  seen  through  the  lens.  Lal)el  the 
three  chambers  shown  locules,  and  the  white,  egg-shaped  objects  within 
ovulesA 

Make  a  longitudinal  section  of  another  ovary,  taking  i)ains  to  secure 
a  good  view  of  the  ovules,  and  sketch  as  seen  through  the  lens. 

(i.  Making  use  of  the  information  already  gained  and  the  cross  section  of 
the  ovary  as  sketched,  construct  a  diagram  of  a  cross  section  of  the 
entire  flower,  showing  the  contents  of  the  ovary. 

II.  Split  a  flower  lengthwise  and  construct  a  longitudinal  section  of  the 
entire  flower. 

46.  The  flower  of  the  buttercup.*  * 

A.  Sketch  the  mature  liower  as  seen  in  a  side  view,  looking  a 
little  down  into  it.  Label  the  pale  greenish-yellowy  hairy 
outermost  parts,  se/?rf/.s-;  the  larger,  bright  yellow  parts  al)(»vt' 
and  within  these,  j-je^aZ.v;  '^'"d.  the  yellow-knobbed  organs  which 
occupy  a  good  deal  of  the  interior  of  the  flower,  stamens. 

B.  Note  the  difference  in  the  position  of  the  sepals  of  a  newly 
opened  flower  and  that  of  the  sepals  of  a  flower  which  has 
opened  as  widely  as  possible.  Note  the  way  in  which  the 
petals  are  arranged  in  relation  to  the  sepals.  In  an  opening 
flower  observe  the  arrangement  of  the  edges  of  the  petals, — 
how  many  entirely  outside  the  others,  how  many  entirely 
inside,  how  many  with  one  edge  in  and  the  other  out. 

(".  Cut  off  a  sepal  and  a  petal,  each  close  to  its  attachment  to 
the  flower ;  place  both,  face  down,  on  a  sheet  of  paper,  and 

•  The  secfiDii  will  l)c  mor.- siil  isfactoiy  if  iii:i.lt'  from  :iii  oM.-r  liuw.-r.  m-own  out 
of  doors,  from  which  the  pciiantli  lias"  falli'ii.  In  this  cast'  lalx-i  the  oiitaiued 
()l)jects  developing  seeds. 


68     STRUCTURE  AND  PHYSIOLOGY  OF  SEED  PLANTS 

sketch  about  twice  the  natural  size  and  label  it  x  2.  Describe 
the  difference  in  appearance  between  the  outer  and  the  inner 
surface  of  the  sepal  and  of  the  petal.  N'ote  the  little  scale 
at  the  base  of  the  petal,  inside.  Lift  up  the  free  edge  of  this 
scale  with  the  point  of  a  needle  and  look  for  nectar. 

D.  Strip  off  all  the  parts  from  a  flower  which  has  lost  its 
petals,  until  nothing  is  left  but  a  slender,  conical  object  a 
little  more  than  an  eighth  of  an  inch  in  length.  This  is 
the  receptacle  or  summit  of  the  flower  stalk. 

E.  In  a  fully  opened  flower  note  the  numerous  yellow-tipped 
stamens,  each  consisting  of  a  short  stalk,  the  filament,  and 
an  enlarged  yellow  knob  at  the  end,  the  anther.  Note  the 
division  of  the  anther  into  two  portions,  which  appear  from 
the  outside  as  parallel  ridges,  but  which  are  really  closed 
cavities  full  of  pollen. 

F.  Observe  in  the  interior  of  the  flower  the  somewhat  globular 
mass  (in  a  young  flower  almost  covered  by  the  stamens). 
This  is  a  group  of  pistils.  Study  one  of  these  groups  in  a 
flower  from  which  the  stamens  have  mostly  fallen  off,  and 
make  an  enlarged  sketch  of  the  head  of  pistils.  Eemove 
some  of  the  pistils  from  a  mature  head,  and  sketch  a  single 
one  as  seen  with  the  magnifying  glass.  Label  the  little 
knob  or  beak  at  the  upper  end  of  the  pistil  stigma,  and  the 
main  body  of  the  pistil  the  ovary.  Make  a  section  of  one  of 
the  pistils,  parallel  to  the  flattened  surfaces,  and  note  the 
partially  matured  seed  within. 

POLLINATION  AND  FERTILIZATION 
EXPERIMENT  XLII 

Production  of  pollen  tubes.*  *  Make  a  hanging-drop  culture 
(Sec.  204),  or  place  a  few  drops  of  suitably  diluted  sirup  of  cane 
sui>ar  (Sec.  170),  with  some  fresh  pollen,  in  a  concave  cell  ground 
in  a  microscope  slide,  and  cover  with  a  thin  glass  circle.  Place 
the  slide  under  a  bell  glass,  with  a  wet  cloth  or  sponge,  to  prevent 


THE   BEAX   Vi)\)  69 

evaporation  of  the  water,  and  set  aside  in  a  warm  place,  or  merely 
put  some  pollen  in  sirup  in  a  watch  crystal  under  the  bell  glass. 
Examine  from  time  to  time  to  note  the  appearance  of  the  pollen 
tubes.  Try  several  kinds  of  pollen  if  possible,  using  solutions  of 
various  strengths.  The  following  kinds  of  pollen  form  tul)es 
readily  in  sirups  of  the  strengths  indicated  : 

Tulip 1  to  3  per  cent 

Narcissus .3  to  5  per  cent 

Cytisus  canariensls  (called  Genista  by  florists)  15  per  cent 

Chinese  primrose 10  per  cent 

Sweet  pea 10  to  1.5  per  cent 

Tropceolum 15  per  cent  i 

Reference.    Strasburger-Hillhouse,  6 


THE  FRUIT  2 

47.  A  capsule  (legume),  the  bean  pod.^  *  * 

A.  Lay  the  pod  flat  on  the  table  and  make  a  sketch  of  it,  about 
natural  size.     Label  stigma,  style,  ovary,  calyx,  flou'er  stalk. 

B.  Make  a  longitudinal  section  of  the  pod,  at  right  angles  to 
the  plane  in  which  it  lay  as  first  sketched,  and  note  the  par- 
tially developed  seeds,  the  cavities  in  which  they  lie,  and 
the  solid  portion  of  the  pod  between  each  bean  and  the  next. 
Split  another  pod,  so  as  to  leave  all  the  beans  lying  undis- 
turbed on  one  half  of  it,  and  sketch  that  half,  showing  the 
beans  lying  in  their  natural  position  and  the  funiculus,  or 
stalk,  by  which  each  is  attached  to  the  2^l(^ce7ita. 

C.  Make  a  cross  section  of  another  pod  through  one  of  the 
beans,  sketch  the  section,  and  label  the  placenta.  Break  off 
sections  of  the  pod  and  determine,  by  observing  where  the 

1  The  sweet-pea  pollen  and  that  of  Tropseolum  are  easier  to  manage  than  any 
other  kinds  of  which  the  authors  have  personal  knowledge.  If  a  concave  slide  is 
not  available,  the  cover  glass  may  be  propped  up  on  hits  of  the  thinnest  broken 
cover  glasses.  From  presence  of  air  or  for  some  other  reason,  the  formation  of 
pollen  tubes  often  proceeds  most  rapidly  just  inside  the  margin  of  the  cover  glass. 

2  If  time  is  not  available  for  all  of  these  studies,  two  or  tliree  types  will  suffice. 

3  Material  in  preservative  fluid  such  as  formalin  will  an.swer,  or  fresh  string 
beans  or  shell  beans  may  be  used. 


70     STIIL'CTURE  AND  IMIYSIOLOGY  OF   SEED   PLANTS 

most  stringy  portions  are  found,  where  the  fibro-vascular 
bundles  are  most  numerous. 
D.  Examine  some  ripe  pods  of  tlie  preceding  year/  and  notice 
where  the  dehiscence,  or  splitting  open  of  the  pods,  occurs, 
whether  down  the  placental  edge,  ventral  suture,  the  other 
edge,  dorsal  suture,  or  both. 

48.  A  schizocarp,  the  fruit  of  caraway.-  Examine  a  complete  fruit, 
"caraway  seed"  (magnified).  If  it  has  not  been  roughly  handled, 
it  should  show  the  remains  of  the  stigmas,  surmounting  the  two 
halves,  merirarps,  of  the  fruit.  The  mericarps  are  borne  on  a 
forked  stalk,  from  which  they  remain  suspended  until  blown 
away  by  the  wind  or  otherwise  detached.  JVlake  a  cross  section 
of  one  mericarp  (if  dry,  after  soaking  it  for  a  minute  or  two  in 
hot  water).  Draw  it  magnified  and  label  the  pericarp,  with  its 
oil  tubes  and  the  seed  within.  The  tubes  contain  the  volatile  oil 
which  gives  the  fruit  its  characteristic  smell  and  flavor. 

This  fruit  has  no  very  effective  means  for  securing  dispersal. 
Compare  it  in  this  respect  with  the  fruits  (commonly  called 
seeds)  of  parsnip  and  of  carrot. 

49.  An  akene,  the  fruit  of  dock. 

A.  Hold  in  the  forceps  a  ripe  fruit  of  any  of  tlie  common  kinds  of  dock, 
and  examine  with  the  lens.  Note  the  three  dry,  veiny,  membranaceous 
sejjals  by  whicli  the  fruit  is  inclosed.  On  the  outside  of  one  or  more 
of  the  sepals  is  found  a  tubercle,  or  thickened  appendage,  which  looks 
like  a  little  seed  or  grain.  Cut  off  the  tubercles  from  several  of  the 
fruits ;  put  these,  with  some  uninjured  ones,  to  float  in  a  pan  of  water, 
and  watch  their  behavior  for  several  hours.  What  is  apparently  the 
use  of  the  tubercle  ? 

Of  what  use  are  the  sepals  after  dryinsj  up  ?    Why  do  tlie  fruits 
cling  to  the  plant  long  after  ripening  ? 

B.  Carefully  remove  the  sepals  and  examine  the  fruit  within  them.  What 
is  its  color,  size,  and  shape  ?  Note  the  three  tufted  stigmas  attached 
by  slender  threads  to  the  apex  of  the  fruit.  What  does  their  tufted 
shape  indicate  ? 

What  evidence  is  there  that  this  seed-like  fruit  is  not  really  a  seed  ? 

1  Preserved  dry  for  the  purpose. 

-  "  Caraway  seeds  "  can  be  bouglit  from  the  druggists. 


THE   LEMOX  71 

C.  Make  a  cross  section  of  a  fruit  and  notice  whether  the  wall  of  the 
ovary  can  be  seen  distinct  from  the  seed  coats.  Compare  tlie  dock 
fruit  in  this  respect  with  the  fruit  of  the  buttercup  shown  in  Prin- 
ciples, Fig.  161.    Such  a  fruit  as  either  of  these  is  called  an  akene. 

50.  A  nut,  the  acorn. 

A.  Sketch  the  entire  acorn,  side  view,  with  the  base  inclosed  in  its  invo- 
lucre, the  "acorn  cup."  Note  the  remains  of  the  stigma  at  the  top  of 
the  acorn. 

B.  Cut  a  cross  section  of  the  acorn  about  midway  of  its  length.  Note 
the  hard  pericarp  and  the  seed,  with  thick  cotyledons. 

C.  Make  a  drawing  of  a  lengthwise  section  of  the  seed  cut  at  right  angles 
to  the  surfaces  where  the  cotyledons  join.  Look  for  the  plumule 
and  the  hypocotyl.  Note  and  describe  the  testa.  Test  the  cotyledons 
for  starch  and  for  oil.  Note  the  taste  of  the  seeds.  How  are  they 
disseminated  ? 

If  possible,  compare  the  acorn  with  such  other  nuts  as  the  chest- 
nut and  the  hazelnut. 

51.  A  berry,  the  tomato. 

A.  Study  the  external  form  of  the  tomato,  and  note  the  persistent  calyx 
and  peduncle. 

B,  Cut  a  cross  section  at  about  the  middle  of  the  tomato.  Note  the 
thickness  of  the  epidermis  (peel  off  a  strip)  and  of  the  wall  of  the  ovary. 
Note  the  number,  size,  form,  and  contents  of  the  cells  of  the  ovary. 
Observe  the  thickness  and  texture  of  the  partitions  between  the  cells. 
Sketch.  What  changes  in  the  fruit  of  the  pepper  {Principles,  Fig.  IGO) 
would  make  it  resemble  a  tomato  ?  Note  the  attachments  of  the  seeds 
to  the  placentas,  and  the  gelatinous,  slippery  coating  of  each  seed. 

The  tomato  is  a  typical  berry,  but  its  structure  presents  fewer 
points  of  interest  than  are  found  in  some  other  fruits  of  the  same 
general  character,  so  the  student  will  do  well  to  spend  a  little  more 
time  on  the  examination  of  such  fruits  as  the  orange  or  the  lemon, 

52.  A  leathery-skinned  berry,  or  hesperidium,  the  lemon.  *  ^  l*ro- 
oure  a  large  lemon  which  is  not  withered  ;  if  possible,  one  which 
still  shows  the  remains  of  the  calyx  at  the  base  of  the  fruit. 

A.  Note  the  color,  general  shape,  surface,  remains  of  the  calyx, 
knob  at  portion  formerly  occupied  by  the  stigma.  Sketch 
the  fruit  about  natural  size. 

B.  Examine  the  pitted  surface  of  the  rind  with  the  lens,  and 
sketch  it. 


I     STKUCTUKE  AM)   I'llYSIOLOGY  OF   SEED  PLANTS 

C.  Remove  the  bit  of  stem  and  dried=up  calyx  from  the  base 
of  the  fruit  ;  observe,  above  the  calyx,  the  disk  on  which 
the  pistil  stood.  jS^ote  with  the  lens  and  count  the  minute 
whitish,  raised  knobs  at  the  bottom  of  the  saucer-shaped 
depression  left  by  the  removal  of  the  disk.    What  are  they  ? 

1).  ^lake  a  transverse  section  of  the  lemon,  not  more  than  a 
fifth  of  the  way  down  from  the  stigma  end,  and  note  : 

1.  The  thick  skin,  pale  yellow  near  the  outside,  white  within. 

2.  The  more  or  less  wedge-shaped  divisions  containing  the 
juicy  pulp  of  the  fruit.  These  are  the  matured  locules  of 
the  ovary  ;  count  these. 

3.  The  thin  partition  between  the  cells. 

4.  The  central  column  or  axis  of  white  pithy  tissue. 

5.  The  location  and  attachment  of  any  seeds  that  may  be 
in  the  section. 

Make  a  sketch  to  illustrate  these  points. 

E.  Study  the  section  with  the  lens  and  note  the  little  spherical 
reservoirs  near  the  outer  part  of  the  skin,  which  contain  the 
oil  of  lemon  which  gives  to  lemon  peel  its  characteristic  smell 
and  taste.  With  the  razor  cut  a  thin  slice  from  the  surface 
of  a  lemon  peel,  some  distance  below  the  section,  and  at  once 
examine  the  freshly  cut  surface  with  a  lens  to  see  the  reser- 
voirs, still  containing  oil,  —  which,  however,  soon  evapo- 
rates. On  the  cut  surface  of  the  pulp  (in  the  original  cross 
section)  note  the  tubes  or  sacs  in  which  the  juice  is  contained. 
These  tubes  are  not  cells,  but  their  walls  are  built  of  cells. 

F.  Cut  a  fresh  section  across  the  lemon,  about  midway  of  its 
length,  and  sketch  it,  bringing  out  the  same  points  which 
were  shown  in  the  previous  one.  The  fact  that  the  number 
of  ovary  locules  in  the  fruit  corresponds  with  the  number  of 
minute  knobs  in  the  depression  at  its  base  is  due  to  the  fact 
that  these  knobs  mark  the  points  at  which  fibro-vascular 
bundles  passed  from  the  flower  stalk  into  the  cells  of  the  fruit, 
carrying  the  sap  by  which  the  growth  of  the  latter  was 
maintained. 


STUDIKS   OF   FRUITS  73 

Note  the  toughness  and  thickness  of  the  seed  coats.  Taste 
the  kernel  of  the  seed. 
G.  Cut  a  very  thin  slice  from  the  surface  of  the  skin,  mount 
in  water,  and  examine  with  a  medium  power  of  the  micro- 
scope. Sketch  the  cellular  structure  shown,  and  compare  it 
with  the  sketch  of  the  cork  of  the  potato  tuber. 

Of  what  use  to  the  fruit  is  a  corky  layer  in  the  skin  ? 

Reference.    Strasburger-Hillhouse,  6. 

53.  A  drupe,  the  cherry.  Make  a  cross  section  of  a  partly  grown  cherry,  in 
which  the  stone  has  not  become  too  hard  to  cut.  Make  a  magnified  sketch 
of  it,  showing  the  double  pericarp,  consisting  of  the  exocarp,  or  fleshy  part, 
covered  witli  a  thin,  tough  epidermis,  and  tlie  endocarp,  or  stone,  containing 
the  seed.     Crack  some  ripe  clierry  stones  and  study  the  seeds. 

If  possible,  compare  with  the  structure  of  tlie  cherry  that  of  other  drupes, 
such  as  the  peach,  the  fruit  of  the  cocoanut  (with  the  husk),  the  entire 
fruit  (with  husk)  of  waliuit,  butternut,  or  hickoiy  nut,  and  the  fruit  of  the 
Cornus,  or  dogwood. 

54.  An  accessory  fruit,  the  strawberry. 

A.  Study  the  flower  of  a  strawberry,  noting  particularly  the  number, 
shape,  and  position  of  the  pistils. 

B.  Examine  a  series  of  strawberry  fruits,^  beginning  at  the  time  when 
the  cluster  of  pistils  shows  signs  of  enlarging.  How  much  does  each 
pistil  enlarge  ?    What  causes  the  increased  size  of  the  fruit  ? 

C.  Study  a  firm,  ripe  strawberry  with  the  lens,  and  draw  the  ripened 

pistils,  called  akenes. 

D.  Cut  a  lengthwise  section  of  the  fruit  and  sketch  it. 

What  is  the  main  difference  in  proportions  between  a  head  of  akenes,  like 
that  in  Principles,  Fig.  161,  and  a  strawberry  ?  What  is  the  use  of  the 
pulpiness  of  the  ripened  receptacle  ■' 

55.  Development  of  a  fruit.  Secure  a  series  of  as  many  stages  as  possible 
in  the  development  of  some  convenient  fruit,  as  the  conmion  bean,  from  the 
newly  fertilized  pistil  to  the  full-grown  pod.- 

A.  Make  drawings  of  the  entire  fruit,  the  earlier  stages  x  4  or  x  5,  but 
all  the  later  ones  natural  size. 

B.  Cut  thin  cross  sections  and  lengthwise  sections  (through  the  seed)  of 
a  series  of  fruits  and  sketch  them,  using  a  magnification  of  about  20 

1  Material  preserved  in  alcohol  will  answer. 

'-  Other  leguminous  fruits,  or  any  moderately  large  capsules  or  berries,  will  an- 
swer. Material  in  preservative  fluid  suffices  for  all  but  the  study  of  the  course  of 
absorbed  liquids. 


74     STRUCTURE   AND   PHYSIOLOGY   OF  SEED   PLANTS 

diameters  for  thv  earliest  ones  and  ten  or  less  for  the  later  ones.  Some 
of  the  sections  may  be  treated  to  advantage  with  potash  solution  and 
acetic  acid  (Sec.  169).  Note  the  changes  in  size  and  shape  of  the  seed, 
in  relative  development  of  seed  coat  and  embryo,  and  in  relative  bulk 
of  the  style,  stigma,  and  ovary  wall  (pod)  compared  with  the  contained 
seeds,  as  the  latter  mature.  After  treatment  with  potash,  several  steps 
in  the  development  of  the  embryo  can  be  made  out  with  m.p.  Note 
that  when  the  developing  seed  is  not  more  than  |  to  i  the  length  of  the 
mature  (dry)  seed,  its  interior  is  mainly  embryo  sac,  with  a  rudimen- 
tary embryo  at  one  end.  Make  several  drawings  to  show  stages  in  the 
process  by  which  the  embryo  grows  until  it  fills  the  sac. 
C.  If  fresh  material  can  be  had,  cut  off  under  water  the  stalk  to  which 
some  well-grown  pods  are  attached.  Transfer  the  stalk  (without 
exposing  the  newly  cut  surface  to  the  air)  into  eosin  solution  and  allow 
it  to  stand  for  an  hour  or  more  in  a  warm,  sunny  place.  Cut  trans- 
verse and  longitudinal  sections  of  the  pods  as  soon  as  they  appear  well 
stained  along  the  edges,  and  slice  off  thin  layers  from  the  flat  surface 
of  a  pod.  Sketch  the  distribution  of  the  fibro-vaseular  bundles  (recog- 
nized by  the  stain)  in  all  the  sections. 

Reference.    Strasburger-Hillhouse,  6. 


Pat?t  TI 
type  studies  preceded  by  the  study 

OF  THE  PLANT  CELL 

THE  PLANT  CELL,  ITS  STRUCTUKE  AND 
REPRODUCTION 

56.  The  cell  structure  of  the  Spirogyra  filament  (App.  6).* 

A.  Examine  living  material.  What  is  its  habit  of  growth, 
floating  or  attached  ?  What  is  its  color  ?  How  does  it  feel 
between  the  fingers  ?  Note  that  it  is  made  up  of  filaments, 
or  threads. 

B.  Mount  two  or  three  filaments  in  water  under  a  cover  glass. 
Examine  with  l.p.  (low  power).  Are  the  filaments  branched  ? 
Do  they  vary  in  thickness  ?  Note  the  cross  partitions  that 
divide  the  filament  into  parts  called  cells.  Draw  the  outline 
of  a  filament  under  l.p. 

C.  Study  a  filament  under  h.p.  (high  power).  Do  the  cells 
vary  in  length  ?  How  much  ?  Select  favorable  cells  and 
focus  on  the  cross  partitions  between  them  to  determine 
their  geometrical  form.  What  is  the  form  of  the  entire 
cell  ?  Draw  a  group  of  two  or  three  cells  on  a  large  scale, 
noting  : 

1.  The   transparent    cell  walls  bounding  the    filament  and 
forming  the  cross  partitions. 

*  To  THE  Instructor  :  The  exercise  outliiuMi  in  See.  HG  is  an  excellent  one  to 
acquaint  the  student  with  the  use  of  the  compound  microscope  and  the  interpre- 
tation of  the  geometrical  form  of  structures  by  focusing  up  and  down.  If  the 
instrument  has  not  been  used  before,  the  student  may  be  made  familiar  with  its 
parts  and  their  manipulation  as  described  on  pages  10-14,  under  the  heading 
"  The  Construction  and  Use  of  the  Compound  Microscope." 

76 


76  TYPE  STUDIES 

2.  The  one  or  more  green  spiral  hands  extending  around  in 
the  interior  of  the  cell  just  under  the  cell  wall.    Focus  on 
the  band  above  and  below,  following  it  around  the  cell. 
D.  Place  a  drop  of  salt  solution  (5  or  10  per  cent)  at  the  side  of 
the  cover  glass,  and  draw  it  under  by  means  of  a  small  piece 
of  filter  paper  applied  against  the  opposite  edge.    Note  the 
contraction  of  a  delicate  membrane  away  from  the  cell  wall, 
so  that  the  former  immediately  becomes  apparent  as  a  con- 
tinuous membrane  inclosing  the  green  band  and  other  contents 
of  the  cell.    This  membrane  and  its  contents  comprise  the 
living  substance,  or  protoplasm,  of  the  Spirogyra  cell,  and  is 
the  living  cell  or  protoplast ;  its  structure  will  be  taken  up  in 
the  next  section.    The  cell  wall  is  composed  of  cellulose  which 
is  not  protoplasmic  in  character,  being  formed  by  the  proto- 
plast and  constituting  a  protective  case  around  it. 
57.  The  structure  of  the  protoplast  of  Spirogyra.*  * 
A.  Mount  a  slide  of  living  Spirogyra  as  described  in  Sec.  56,  B, 
to  study  the  protoplast.    Note  under  h.p.  : 

1.  That  each  green  spiral  band,  called  a  chromatophore,  con- 
tains several  denser  structures  termed  pyrenoids. 

2.  A  globular  or  elliptical  structure,  the  nucleus,  near  the 
center  of  the  cell,  held  in  position  by  delicate  protoplasmic 
strands  which  radiate  outward  to  the  cell  walls.  The  out- 
line of  the  nucleus  will  probably  be  clearer  when  the 
material  is  stained  with  iodine,  as  described  in  B. 

3.  A  delicate  lining,  or  plasma  membrane,  next  the  cell  wall 
under  which  the  chromatophore  lies  imbedded  in  a  layer 
of  protoplasm.  The  plasma  membrane  was  demonstrated 
when  the  protoplast  was  drawn  away  from  the  cell  wall 
by  the  salt  solution,  as  described  in  Sec.  56,  D. 

4.  That  the  interior  of  the  protoplast  contains  no  solid  or 
semifluid  substance,  except  possibly  some  minute  granules, 
and  must  consequently  be  either  liquid  or  gas.  Which 
alternative  is  suggested  by  the  experiment  with  the  salt 
solution  (Sec.  56,  D)  ? 


CELL  STRUCTUKE  OF  SPIROGYRA  77 

Draw  a  large  figure  of  a  cell  showing  the  cell  walls,  plasma 
membrane,  chromatophore  with  pyrenoids,  nucleus  held  in 
place  by  the  radiating  protoplasmic  strands,  and  the  large 
space  in  the  interior  of  the  cell  free  from  protoplasm. 

B.  Place  a  drop  of  iodine  solution  (Sec.  169)  at  the  side  of  the 
cover  glass,  and  draw  it  under  by  means  of  a  small  piece  of 
filter  paper  applied  against  the  opposite  edge. 

1.  Note  the  coloration,  or  staining,  of  the  protoplasmic  struc- 
tures. The  nucleus  usually  stands  out  sharply,  and  should 
be  drawn  if  it  was  not  clearly  seen  in  the  unstained  living 
cell  described  in  A. 

2.  Draw  a  portion  of  the  chromatophore  showing  a  pyrenoid 
under  the  highest  magnification.  There  will  probably 
be  found  a  circle  of  dark  granules  around  the  pyrenoid. 
These  are  starch  grains,  manufactured  by  the  chromato- 
phore in  the  presence  of  sunlight,  the  process  being  called 
photosynthesis. 

C.  Plasmohjsis.  The  shrinking  of  the  protoplast  away  from  the 
cell  wall  when  the  cell  is  bathed  in  a  denser  solution,  as  that  of 
salt  (described  in  Sec.  6Q,  D),  is  Cd^W^diplasmolysis.  Plasmoly sis 
is  accomplished  by  the  withdrawal  of  water  from  the  interior 
of  the  protoplast  through  the  permeable  plasma  membrane 
and  cell  wall  when  there  is  a  denser  solution  outside  of  the 
cell.  Such  a  movement  of  water  through  a  permeable  mem- 
brane is  due  to  osmosis  {Principles,  Sec.  48).  The  plasma 
membrane  of  the  protoplast  is  normally  held  against  the 
cell  wall  in  the  living  cell  by  pressure  from  within,  and  that 
condition  is  called  cell  turgor.  The  fluid  within  the  proto- 
plast IS  termed  cell  sap  and  is  contained  in  cavities  called 
vacuoles.  The  cell  sap  of  Spirogyra  is  in  one  large  vacuole 
occupying  the  central  region  of  the  cell,  in  which  the  nucleus 
is  swung  like  a  hammock  by  radiating  strands  of  proto- 
plasm. If  the  facts  and  principles  illustrated  by  plasmolysis 
in  Spirogyra  are  not  clear,  repeat  the  experiment  outlined  in 
Sec.  5&.  D. 


78  TYPE  STUDIES 

D.  Place  some  living  Spirogyra  in  alcohol  and  after  several  hours 
note  the  extraction  of  a  green  pigment,  chlorophyll^  from  the 
chromatophores  in  the  filaments.  What  change  in  the  color  of 
the  filaments  ?  The  alcohol  may  be  evaporated  by  gentle  heat 
in  a  shallow  dish,  leaving  the  chlorophyll  as  a  green  residue. 

58.  Photosynthesis  in  Spirogyra. 

A.  Perform  the  experiment  in  photosynthesis  outlined  in  Exp,  XXXI, 
using  Spirogyra  for  tlie  subject. 

B.  Place  Spirogyra  for  a  day  or  two  in  the  dark  and  then  test  for  starch 
as  described  in  Sec.  57,  B,  2.  Return  the  material  to  sunlight,  and  after 
several  hours  test  again.     Compare  results. 

59.  Cell  reproduction  in  Spirogyra.  New  cells  arise  in  Spirogyra 
either  (1)  by  cell  division  or  (2)  by  cell  unions  to  form  reproduc- 
tive cells  called  zygospores  or  zygotes. 

60.  Cell  division  in  Spirogyra.  Search  a  slide  of  Spirogyra  for 
adjacent  cells  in  the  same  filament  considerably  shorter  than  the 
average  size.  Such  a  pair  will  probably  be  sister  or  daughter  cells 
formed  by  the  division  of  a  mother  cell.  The  division  of  the 
mother  cell  is  preceded  by  the  division  of  the  nucleus,  after 
wliich  a  partition  wall  of  cellulose  is  formed  between  the  daughter 
nuclei.  Spirogyra  is,  however,  not  a  favorable  subject  for  the 
study  of  nuclear  and  cell  division  (Sec.  (S^). 

61.  Cell  unions  to  form  zygospores  in  Spirogyra.*  *  At  times 
Spirogyra  fruits.^  , 

A.  If  living  material  is  available,  note  the  frequent  change 
in  color  and  occasional  dirty  appearance  of  the  filaments. 
Mount  fruiting  material  (either  living  or  preserved)  teased 
out  well.    Note : 

1.  That  certain  cells  contain  thick-walled  oval  or  elliptical 
structures  densely  filled  with  protoplasm  and  food  material. 
These  are  zygospores  or  zygotes. 

2.  That  the  zygospores  are  formed  by  the  union  or  conjuga- 
tion of  cells.  In  some  species  of  Spirogyra  the  cell  unions 
are  between  different  filaments,  in  other  species  between 

1  The  tevuvs,  fruit  and  fructification  will  be  used  in  Part  II  in  an  uutechnical 
sense  to  designate  various  forms  of  reproductive  organs  and  processes. 


ZYGOSPORE  FORiAIATION   IN   SPIROGYRA  79 

adjacent  cells  of  the  same  filament.  If  the  conjugation  is 
between  different  filaments,  are  the  zygospores  all  formed 
on  one  side  or  are  some  formed  in  the  cells  of  one  filament 
and  some  in  the  other  ? 
B.  Find  and  draw  a  number  of  stages  under  h.p.  illustrating 
the  history  of  the  cell  union  or  conjugation.    Note  : 

1.  That  the  union  takes  place  through  processes  put  out 
from  adjacent  cells.    These  unite  to  form  a  connecting  tube. 

2.  That  the  protoplast  from  one  cell  passes  into  the  other 
and  fuses  with  its  protoplast. 

3.  That  the  product  of  this  cell  union  is  a  fusion  protoplast, 
which  forms  a  heavy  wall  about  itself,  thus  becoming  a 
well-protected  reproductive  cell  or  spore.  Note  the  changed 
appearance  of  the  contents  of  the  spore,  and  the  presence 
of  food  material.    Test  for  starch. 

Cell  unions  of  this  character  are  sexual  processes.  The  cells 
which  unite  are  called  gametes  and  their  product  is  a  sexually 
formed  fusion  cell.  The  fusion  cell  in  Sjnrogyra  is  called  a  zygo- 
sjjore,  or  zygote,  because  the  gametes  are  similar.  For  this  reason, 
also,  this  type  of  sexual  reproduction  is  called  isogamy  (meaning 
similar  gametes). 

Eeference  (on  the  plant  cell).    Principles,  Chap.  XVIII. 

Questions.*  Describe  the  cell  structure  of  Spirogyra.  What 
part  of  it  is  living  substance  and  what  part  of  it  is  non- 
living ?  Why  are  the  cross  walls  in  the  filament  fiat  planes  ? 
What  would  you  expect  to  be  the  form  of  the  wall  at  the 
free  end  of  a  filament?  How  are  new  filaments  of  Sjn- 
rogyra  formed  ?  How  do  the  filaments  grow  and  is  the 
growth  confined  to  any  special  region  ?  W^hat  are  the  essen- 
tial features  in  the  formation  of  zygospores  which  define 
it  as  a  sexual  process  ?     What  part  does  the  zygospore  play 

*  To  THE  Instructor:  The  sets  of  questions  presented  in  conueotion  wltli  the 
type  studies  of  Part  II  are  intehded  to  brin^  before  the  student  fundauu-ntal 
principles  in  connection  with  his  lalwratory  and  HeUl  work,  and  his  reading. 
VVntten  or  oral  exercises  may  be  planned  on  them  if  desired. 


80  TYPE   STUDIES 

in  the  life  history  of  the  plant?  How  is  it  adapted  for 
its  purposes  ?  Construct  a  series  of  diagrams  that  will 
outline  the  life  history  of  Spirogyra.  What  are  believed 
to  be  some  of  the  advantages  to  an  organism  in  having  a 
method  of  sexual  reproduction? 

62.  Cell  structure  of  the  moss  leaf  compared  with  Spirogyra. 

A.  Mount  a  moss  leaf  in  water  and  draw  a  group  of  cells  under  h.p.,  and 
show  details  of  protoplasmic  structure  in  one  of  them.     Note  : 

1.  That  the  chlorophyll  is  contained  in  numerous  small,  disk-shaped 
bodies  called  chloroplasts.    How  are  they  distributed  in  the  cell  ? 

2.  The  multiplication  of  the  chloroplasts  by  simple  constriction.  Draw 
stages  showing  their  division. 

B.  Plasmolyze  the  cells  with  salt  solution,  and  draw  a  group.  Why  do 
adjacent  cells  have  flat  side  walls  '? 

C.  Stain  with  iodine. 

1.  Where  are  starch  grains  formed  ?    Draw. 

2.  Where  does  the  nucleus  lie  ? 

3.  How  much  of  the  cell  is  filled  with  cell  sap  ? 
93.  The  Amoeba  (App.  7). 

A.  Gather  with  a  pipette  some  of  the  slime  at  the  bottom  or  scum  on 
the  top  of  a  culture  of  AmoebcB.  Search,  under  m.p.,  for  transparent, 
naked  cells  which  slowly  change  their  outline,  by  thrusting  out  some 
processes,  pseudopodia,  and  withdrawing  others. 

B.  Stvidy  under  h.p.  the  changes  in  form  of  an  Amoeba  as  it  slowly  moves 
along,  making  a  series  of  outline  sketches.  Note  the  flow  of  the  gran- 
ular cytoplasm  into  the  pseudopodia  as  they  are  formed. 

C.  Draw  diagrammatically  an  individual  on  a  large  scale,  showing: 

1.  The  plasma  membrane,  colorless  and  without  granules. 

2.  The  granular  cytoplasm  inclosed  by  the  plasma  membrane,  fre- 
quently containing  food  inclusions,  as,  for  example,  one-celled  plants 
such  as  diatoms  and  desmids.  How  would  you  expect  this  food  to 
be  taken  into  the  interior  of  the  Amoeba  ? 

8.   A  dense  spherical  nucleus  (not  always  easily  found). 

4.  Vacuoles  which  form,  and  later  suddenly  disappear,  and  consequently 
are  called  contractile  vacuoles. 

D.  The  Amoeba,  as  is  generally  the  case  with  an  animal  cell,  is  a  naked 
protoplast.  Compare  with  a  typical  plant  cell.  What  does  one  have 
that  is  lacking  in  the  other  t^    What  do  both  have  in  common  ? 

The  Amoeba  reproduces  by  construction,  a  single  individual  thus  forming 
two  similar  daughter  Armjcboi  (see  Principles.  Fig.  107.  B). 


NUCLEAR  AND  CELL   DIVISION  81 

64,  Circulation  of  protoplasm  in  the  cell.  Use  Eludea,  or  Nitella,  or  stamen 
hairs  of  Tradescantia. 

A.  Mount  young  leaves  of  Elodea  in  water.  Examine  tlie  simple  cell 
structure  and  find  a  favorable  region  for  detailed  study. 

1.  Note  the  position  and  form  of  the  chloroplasts,  the  nucleus,  the  cyto- 
plasm, comparing  with  previous  studies  on  plant  cells. 

2.  Study  the  circulation  of  protoplasm  next  the  wall  of  the  cell.  Focus 
on  a  chloroplast  as  it  moves  along,  trace  its  path  in  a  simple  sketch 
or  diagram,  and  determine  how  long  it  ta.kes  to  travel  a  certain 
distance  measured  with  the  micrometer.  Warm  the  slide  gently. 
What  is  the  effect  upon  the  rate  of  movement  ?  Describe  the 
movement  carefully.  Is  the  direction  the  same  in  all  cells  ?  Does 
the  substance  of  the  plasma  membrane  move,  or  is  it  granular 
cytoplasm  under  the  membrane  ? 

B.  Mount  a  portion  of  the  stem  of  Nitella,  including  uninjured  internodal 
cells.  Note  the  line  called  the  neutral  zone^  free  from  chloroplasts, 
which  runs  diagonally  across  the  ceU.  The  protoplasm  on  either  side 
of  this  line  moves  in  opposite  directions  (see  Principles,  Sec.  230). 

C.  Cut  the  stamens  out  of  an  opening  flower  or  large  bud  of  Tradescantia 
and  mount  in  water.  The  stamen  hairs  are  chains  of  large  and  very- 
beautiful  cells  in  which  the  nucleus  and  arrangement  of  the  cytoplasm 
may  be  seen  with  especial  clearness.  Are  there  chloroplasts  present  ? 
What  gives  the  peculiar  reddish  violet  color  to  the  cell  ? 

Draw  a  cell  on  a  large  scale  under  h.p.  and  show  the  position  of  the 
nucleus,  and  the  moving  streams  of  protoplasm,  and  indicate  the 
directions  of  the  flow  by  arrows. 

65.  Nuclear  and  cell  division  in  the  root  tip  of  an  onion  or  other  region  of 
growth  (App.  8).  The  details  of  nuclear  structure  and  nuclear  division, 
called  initosis,  can  only  be  studied  in  material  carefully  killed  and  hardened 
to  preserve  the  soft  protoplasm  as  nearly  as  possible  in  its  normal  condition. 
Thin  sections  must  be  cut  with  an  instrument  called  the  microtome  and  these 
stained  to  differentiate  the  protoplasmic  structure  (Sec.  211).  One  of  the 
best  stains  is  a  combination  of  safranin  (red)  and  gentian  violet  (blue). 

A.  Examine  sections  under  l.p.  to  determine  the  relation  of  regions  or 
tissues,  and  diagram  the  position  of  the  root  cap,  the  undifferentiated 
embryonic  tissue  at  the  growing  point,  and  the  beginnings  of  the  differ- 
entiation which  appears  back  of  the  growing  point. 

B.  Select  a  typical  well-stained  cell  in  the  resting  condition.  Draw  under 
h.p.  and  note  : 

1.  The  nucleus  with  one  or  more  deeply  stained  globules,  each  of  which 
is  a  nucleolus,  or  nucleole ;  a  loose  network  containing  chromatin; 
tlie  nuclear  membrane  :  tlu'  nucltawavity  v;\w\\  contains  nuclear  sap. 


82  TYPE   STUDIES 

2.  The  cytoplasm,  granular  in  structure,  probably  containing  one  or 
more  vacuoles  which  were  filled  with  cell  sap. 

3.  The  cell  walls  separating  the  protoplasts  from  one  another. 

C.  Find  a  nucleus  in  the  midst  of  division  (metaphase  of  mitosis).    Note  : 

1.  That  the  chromatin  has  become  organized  into  a  number  of  rod- 
shaped  bodies,  chromosomes,  which  are  grouped  in  the  center  of  the 
cell,  and  that  the  nuclear  membrane  has  disappeared.    Draw. 

2.  That  the  chromosomes  are  arranged  in  a  plate,  equatorial  plate,  be- 
tween the  poles  of  a  sjnndle  composed  of  delicate  spindle  fibers.  Try 
to  count  the  chromosomes. 

3.  Search  for  evidence  of  a  lengthwise  division  of  the  chromosomes 
into  daughter  chromosomes.     Draw. 

D.  Find  a  cell  in  which  the  daughter  chromosomes  have  separated  into 
two  sets  and  are  passing  towards  or  have  been  gathered  at  the  poles  of 
the  spindle  (anaphase  of  mitosis).    Note  : 

1.  The  separation  of  the  daughter  chromosomes  into  two  groups  and 
their  passing  to  the  poles  of  the  spindle  to  form  the  daughter  nuclei. 
Try  to  count  the  chromosomes  in  each  daughter  group  and  compare 
with  the  count  at  the  equatorial  plate.    Draw. 

2.  The  persistence  of  the  spindle  between  the  groups  of  daughter 
chromosomes. 

3.  The  appearance  of  a  delicate  plate  across  the  spindle,  finally  reach- 
ing the  sides  of  the  cell.  This  is  the  cell  plate  and  marks  the  position 
of  the  new  cell  wall  which  will  be  formed,  dividing  the  mother  cell 
into  two  daughter  cells,  each  with  a  nucleus.    Draw. 

E.  Find  a  later  stage  after  the  daughter  nuclei  have  become  organized  as 
resting  nuclei  and  the  cell  division  is  completed. 

F.  Study  the  beginnings  of  nuclear  division  (prophase  of  mitosis)  before 
the  spindle  is  formed  and  the  chromosomes  are  gathered  at  the  equa- 
torial plate  (metaphase).    Note  : 

1.  That  the  loose  chromatin  network  becomes  a  thread,  spirem. 

2.  That  this  thread  divides  transversely  into  segments,  which  are  the 
chromosomes.    Draw. 

3.  That  the  spindle  is  developed  from  accumulations  of  protoplasm 
(kinoplasm)  at  two  poles  outside  of  the  nuclear  membrane.    Draw. 

66.  Characteristics  of  some  organic  compounds  found  in  plant  cells. 

Certain  organic  compounds  will  be  met  so  frequently  in  cell 
studies  upon  the  lower  plants  that  some  of  their  characteristics 
should  be  known.  They  fall  into  two  great  classes  :  (1)  the  carho- 
]i7jdmtes,  composed  of  carbon,  oxygen,  and  hydrogen,  represented 


EUGLENA  83 

by  starch,  sugar,  cellulose,  oils,  and  fats ;  and  (2)  the  proteids, 
which  contain  nitrogen,  sulphur,  and  in  some  cases  phosphorus, 
in  addition  to  carbon,  oxygen,  and  hydrogen.  The  principal  tests 
for  these  substances  and  some  characteristics  of  their  appearance 
are  given  in  Part  I  as  follows  :  (1)  starch,  Sec.  12,  A;  (2)  sugar. 
Sec.  12,  B  ;  (3)  cellulose.  Sec.  12,  C  ;  (4)  oils  and  fats,  Sec.  12,  E  ; 
(5)  proteids.  Sec.  12,  F. 

THE  FLAGELLATES,  OR  FLAGELLATA 

67.  Euglena  (App.  9).     Study  its   habits  in  a  glass  dish  placed  near  a 
window.     Do  the  organisms  congregate  in  any  part  of  the  dish  ?    Why  ? 

A.  Mount  in  a  drop  of  water  and  examine  under  l.p.  Describe  move- 
ments.   Under  h.p.  study  cell  structure.    Note  and  draw  : 

1.  The  naked  protoplast  ;  arrangement  and  form  of  the  chloroplasts. 

2.  A  red  pigment  spot  at  the  forward  end.  Can  you  suggest  its  pos- 
sible function  with  reference  to  the  behavior  of  the  organism 
towards  light  ? 

3.  The  structure  of  the  forward  end  with  a  narrow,  slit-like  opening 
leading  into  a  cavity  ;  the  position  of  a  long,  \m\v-\\\e  flagellum,  or 
cilium.  These  structures  will  probably  become  clearer  after  staining 
with  iodine,  as  described  in  B. 

B.  Drain  off  as  much  water  as  possible  from  under  the  cover  glass  and 
then  place  a  drop  of  iodine  solution  at  the  side.  It  will  slowly  diffuse 
through  the  water,  killing  and  staining  the  Euglenw.  Watch  and  de- 
scribe the  effect.  Draw  details  of  the  forward  end,  showing  the  flagel- 
lum  and  the  opening. 

C.  Study  Euglena  in  the  encysted  condition,  when  the  protoplast  is  sur- 
rounded by  a  protective  wall.  Search  for  examples  of  cell  division 
while  in  this  condition.    Draw. 


THE  SLIME  MOLDS,  OR  MYXOMYCETES 

68.  The  spore  fruit  of  a  slime  mold.  The  fructifications  of  the  slime  molds 
are  certainly  plant-like  and  have  been  studied  and  classified  chiefly  by  bot- 
anists. Such  types  as  Stemonitis,  ArcT/ria,  Hemitrichia,  and  Lycogola  are 
favorable  for  study. 

A.,  Draw  a  habit  sketch  of  the  spore  fruit.     Note  : 

1.  The  character  of  the  attachment,  whether  or  not  stalked  ;  the  spore 
case. 


84  TYPE  STUDIES  * 

2.  The  wall  of  the  spore  case.    Has  it  a  cellular  structure  ? 

3.  The  thread-  or  net-like  structure,  capillitium,  within  the  spore  case 
and  the  powdeiy  spore  mass, 

B.  Under  h.p.  draw  a  portion  of  the  capillitium,  showing  markings,  and  a 
group  of  spores. 

69.  The  Plasmodium.  This  stage  in  the  life  history,  when  available,  may 
be  made  the  subject  of  very  interesting  studies  on  the  structure  and  behavior 
of  protoplasm. 

A.  Mount  a  small  portion  and  examine  under  low  and  high  powers.  Note 
its  consistence,  structure,  and  contents.  Describe  and  identify  the  food 
contents  as  far  as  possible.  Is  starch  present  ?  Are  oils  or  fats  pres- 
ent ?  Do  you  find  any  microscopic  organisms  which  have  been  ingulfed 
by  the  Plasmodium? 

B.  Place  the  Plasmodium  on  moist  blotting  paper  under  a  bell  glass. 
Devise  experiments  to  determine  its  reaction : 

1.  To  bright  illumination  coming  from  one  direction,  with  darkness 
or  faint  illumination  on  the  other  side. 

2.  To  warmth  on  one  side. 

3.  To  moisture  on  one  side  contrasted  with  dryness  on  the  other. 

C.  Should  the  plasmodium  begin  to  fructify,  trace  and  describe  the  devel- 
opment of  the  spore  cases. 

70.  The  flagellate-like  stage  of  a  slime  mold.  Try  to  germinate  fresh  spores 
in  a  hanging  drop  (Sec.  204)  or  a  covered  watch  glass.  Use  water  in  which 
decaying  wood  has  been  soaked.  Study  the  structure  and  habits  of  the 
motile  protoplasts  derived  from  the  spores  ;  also  the  amoeboid  condition, 
myxamoeboe,  which  follows,  and  trace  if  possible  the  union  of  the  myxa- 
mcebse  to  form  a  new  plasmodium. 

Reference  (to  slime  molds).    Macbride,  38. 

THE  BLUE-GREEN  ALG^,  OR  CYANOPHYCEiE 

71.  Field  work  on  the  blue-green  algae.  Good  displays  of  the  blue-green 
algse  may  be  found  in  open  drains  and  stagnant  jdooIs  which  are  somewhat 
foul.  Ditches  and  pools  in  salt  marshes  will  furnish  excellent  material. 
Slimy,  dark  green  growths  on  the  surface  of  damp  flowerpots,  woodwork, 
and  earth  are  frequently  composed  of  these  growths.  Water  blooms  are 
generally  made  up  of  either  blue-green  algfe  or  Euglena. 

Make  collections  in  bottles,  carefully  noting  the  habitat,  and  bring  to  the 
laboratoi-y  for  study. 

72.  Unicellular  blue-green  algae.  Material  of  Glceocapsa  or  Chroococcus^ 
Clathrocystis  or  Crelosphceriuin  is  excellent.    Study  and  draw  : 

1.  The  form  and  arrangement  of  the  cells  and  cell  colonies. 


OSCILLATOKIA  85 

2.  The  structure  of  cellular  envelopes  if  present. 

8.  The  detailed  structure  of  a  cell  ;  the  color  and  its  distribution.    Are 

chromatophores  present  ?    Can  you  find  a  nucleus  ?    How  do  the  cells 

multiply  ;' 

73.  Oscillatoria.*^ 

A.  Place  a  small  mass  of  material  in  a  watch  glass  full  of 
water.  What  is  the  color  ?  After  a  few  hours  observe  the 
filaments  radiating  out  from  the  central  mass.  Explain  this 
habit  of  growth  after  the  study  outlined  in  B. 

B.  Mount  material  well  teased  out.    Under  l.p.  note : 

1.  The  filaments.  Are  they  branched  or  unbranched  ?  Are 
they  of  uniform  diameter  ? 

2,  The  movements  of  the  filaments.    Describe  and  diagram. 

C.  Under  h.p.  note  and  illustrate  : 

1.  The  cell  structure  at  the  tip  of  a  filament  and  the  par- 
tition walls  back  of  the  tip.  Compare  the  length  and 
breadth  of  the  cells.    What  is  their  geometrical  form  ? 

2.  Draw  a  group  of  cells  on  a  large  scale,  showing  the  dis- 
tribution of  their  granular  contents  and  the  coloring 
matter.  Are  chromatophores  present  ?  Can  you  find  a 
nucleus  ?    Where  are  new  partition  walls  formed  ? 

3.  Note  the  occasional  dead  cells.  What  is  the  form  of  the 
cell  wall  on  adjacent  living  cells  and  at  the  free  tips  of 
filaments  ?  Why  should  the  wall  take  this  form  ?  The 
presence  of  the  dead  cells  weakens  the  filament,  which 
breaks  apart  readily  at  these  points. 

4.  How  do  the  cells  multiply,  and  how  are  new  filaments 
formed  ?  Is  cell  division  confined  to  any  particular  region, 
or  is  it  general  throughout  the  filament  ? 

5.  Search  for  a  very  delicate  sheath  which  holds  the  cells 
together  in  a  filament,  like  paper  about  a  roll  of  coins. 

D.  Should  material  of  Lyngbya  be  available,  it  may  be  studied 
advantageously  at  this  point  in  comparison  with  Oscillatoria. 

E.  Dry  a  mass  of  Oscillatoria  thoroughly,  then  pulverize  and 
place  in  a  test  tube  with  twice  its  bulk  of  water.     After 


5  TYPE  STUDIES 

several  hours  describe  the  color  of  the  water  as  seen  by 
transmitted  lighi  and  by  reflected  light.    This  color  is  due 
to  the  pigment  characteristic  of  the  blue-green  algae, 
74.  Nostoc  or  Anabaena. 

A.  Study  the  form  and  consistency  of  the  colonies  of  Nostoc 
Make  a  habit  sketch.  Cut  out  a  small  portion  from  a  colony 
and  crush  under  a  cover  glass.    Note  under  l.p. : 

1.  The  chains  of  cells,  or  filaments,  imbedded  in  the  almost 
colorless  jelly. 

2.  Are  the  filaments  branched  ?  continuous  ? 

B.  Under  h.p.  draw  part  of  a  filament,  showing : 

1.  The  vegetative  cells,  their  attachment  to  one  another, 
method  of  multiplication,  and  the  character  of  the  proto- 
plasmic contents. 

2.  The  occasional  enlarged  cells,  heterocysts,  empty  or  almost 
empty  of  cell  contents.  Two  button-like  plugs  at  the  ends 
of  the  heterocysts,  which  close  what  were  formerly  very 
small  openings  into  the  adjacent  vegetative  cells.  How 
are  the  heterocysts  distributed  throughout  the  filaments  ? 
From  what  are  they  developed  ?  Their  function  is  not  well 
known,  but  the  filaments  tend  to  break  apart  at  either  side 
of  these  cells.    How  then  are  new  filaments  formed  ? 

C.  Material  of  Anabcena  with  resting  cells,  or  spores,  is  more 
interesting  than  Nostoc,  and  furnishes  an  excellent  compara- 
tive study  with  that  type,  or  may  be  substituted  for  it.  Study 
the  general  morphology  as  in  Nostoc,  and  especially  the  struc- 
ture, position,  and  development  of  the  resting  cells. 

Reference  (on  the  blue-green  algae).  Princijyles,  Sees.  207-211. 

Questions.  What  are  some  of  the  life  conditions  under  which 
the  blue-green  algae  live  ?  Describe  the  life  history.  How 
may  forms  without  differentiated  resting  cells,  or  spores  (as 
Oscillatoria),  survive  unfavorable  seasons  of  drought  or  win- 
ter ?  In  what  respects  is  the  cell  structure  of  these  plants 
simpler  than  that  of  Spirogyra  ?  Compare  the  morphology 
of  the  blue-green  algae  with  that  of  the  bacteria  (if  studied). 


PLEUROCOCCUS  87 

75.  Tolypothrix  or  Scytonema.  Tlieso  types  are  especially  interesting  for 
the  peculiar  method  of  branching,  culled  false  branching .  Study  the  general 
morphology  of  the  filament  with  special  reference  to  the  relation  of  the 
branches  to  the  heterocysts.  Find  the  beginnings  of  a  branch  and  note  that 
it  breaks  through  the  sheath  which  incloses  the  vegetative  cells.  The 
heterocysts  are  more  or  less  firmly  united  to  the  sheath,  while  the  vegeta- 
tive cells  may  slip  along  within  it.  The  multiplication  and  growth  of  the 
vegetative  cells  between  the  heterocysts,  as  fixed  points,  bring  pressure  to 
bear  which  results  in  the  rupture  of  the  sheath  and  formation  of  a  branch. 

76.  Gloeotrichia.  This  type  should  be  studied  chiefly  for  the  remarkable 
resting  cells^  or  spores,  formed  next  the  heterocysts  at  the  bases  of  the  radiat- 
ing filaments,  and  for  the  attenuation  of  the  filaments  into  long  hairs. 


THE  GREEN  ALG^,  OR  CHLOROPHYCE^ 

77.  Field  work  on  the  green  algae.  The  green  algfe  live  under  a  variety  of 
conditions,  with  several  characteristic  habitats  :  (1)  there  are  the  growths 
in  clear  pools  and  ponds  with  floating  filamentous  masses  (pond  scums),  free- 
swimming  forms  (members  of  the  Volwx  family),  attached  filamentous  or 
expanded  types  {CEdogoniwn,  Vaucheria,  Choitophora,  CuleochcBte,  etc.),  smd 
the  sediment,  rich  in  desmids,  diatoms,  and  many  other  one-celled  types  ; 
(2)  there  are  the  growths  in  slowly  running  water  of  streams  and  on 
the  borders  of  lakes  (frequently  Ulothrix,  Stigeoclonium,  Draparnaldia, 
Cladophora,  and  the  stoneworts)  ;  (3)  there  are  the  growths  just  above  and 
below  low-water  mark  on  rocks  along  the  seacoast  (chiefly  sea  lettuces, 
Ulothrix,  and  Cladophora)  ;  (4)  there  are  the  slimy  growths  on  the  trunks  of 
trees  and  stone  walls  {Pleurococcus  and  other  one-celled  relatives),  and 
filamentous  forms  on  the  earth  (Vaucheria). 

Studies  should  be  made  of  some  of  these  habitats,  collections  gathered 
and  examined  in  the  laboratory,  and  the  principal  genera  identified.  Notes 
should  be  taken  in  the  field  describing  the  appearance  of  the  algte  as  regards 
size,  texture,  and  color,  and  their  growth  habits  in  relation  to  light,  depth 
of  immei-sion,  and  other  factors. 

78.  Pleurococcus.*  *  Gather  pieces  of  green  stained  bark  from 
the  north  side  of  trees,  or  scrapings  from  old  fences. 

A.  Note  the  color  and  powdery  appearance  of  the  growth  over 
the  surface  and  its  thickness  in  places  where  the  growth 
separates  as  small  scales.  Moisten  the  bark  and  note  the 
brighter  color. 


88  TYPE   S'PUDrKS 

B.  Scrape  off  some  of  the  moistened  Pleurococcus  and  mount  in 
water,  well  teased  out.  Examine  under  l.p.  to  find  favorable 
material.    Under  h.p.  draw  : 

1.  Groups  of  cells  in  outline,  showing  their  loose  attachment 
to  one  another,  except  just  after  cell  division,  when  the 
(laughter  cells  are  to  be  found  in  pairs. 

2.  A  single  large  cell,  showing  the  cell  wall  and  the  proto- 
plast;  a  nucleus  can  often  be  distinguished  in  the  center 
of  the  protoplast,  and  the  chlorophyll  is  generally  held  in 
a  single  large  cliromatophore  which  may  or  may  not  have  a 
pyrenoid.  These  points  are  brought  out  more  clearly  by 
staining  with  iodine. 

Questions.  In  what  respects  is  the  cell  structure  of  Pleuro- 
coccus higher  than  that  of  the  blue-green  algse  ?  What  is  the 
life  history  of  Pleurococcus  ?  Is  it  easily  killed  by  winter's 
cold  and  summer's  drought,  judging  from  its  appearance  on 
trees  and  in  other  situations  ?  Make  a  study  of  the  distri- 
bution of  Pleurococcus  on  a  tree  trunk,  noting  the  limits  of 
growth  and  the  regions  of  its  greatest  luxuriance.  Try  to 
determine  the  reasons  for  the  limits  of  growth. 

79.  Sphaerella  or  Volvox  (App.  10).  These  types  and  others  of  the  Volvox 
family,  when  available,  are  especially  interesting  for  their  life  habits  and 
cell  structure,  and  in  the  higher  types  for  the  complex  cell  colonies  and 
methods  of  sexual  reproduction. 

A.  In  water  swarming  with  Sphaerella  note  the  reaction  of  the  organism 
to  light  when  the  vessel  is  placed  near  a  window^ 

B.  Under  h.p.  study  the  movements  of  the  cell  and  the  cell  structure, 
later  killing  and  staining  with  iodine  as  described  for  Euglena 
(Sec.  67,  B).     Note  and  draw  : 

1.  The  thick,  somewhat  gelatinous  cell  wall. 

2.  The  protoplast  with  two  cilia.^  red  pigment  spot,  and  large  chromato- 
phore.    AVhich  is  the  forward  end  as  the  organism  swims  ? 

C.  Should  gametes  be  developed  and  begin  to  conjugate,  or  should  the 
large  vegetative  cells  form  thick-walled  resting  cells,  these  processes 
may  be  studied. 

D.  Volvox  as  an  example  of  a  very  highly  organized  cell  colony  may  be 
compared  with  Sphaerella  or  other  one-celled  forms  of  the  same  family. 


ULOTITPJX  89 

Study  its  swimming  habits  and  its  reaction  to  light  in  a  vessel.  Note  the 
points  of  similarity  of  its  protoplasts  to  the  cells  of  Sphoerella.  .Study 
the  structure  of  the  cell  colony  and  the  method  of  forming  daughter 
colonies.  Study  the  development  of  the  eggs  and  their  change  into 
oospores  after  fertilization,  and,  when  material  is  present,  the  forma- 
tion of  the  packets  of  sperms.  Stained  preparations  may  be  studied 
(Sec.  212). 
References  (on  the  Volvox  family).  Goebel,  16,  p.  34 ;  Engler  and  Prantl, 
39 ;  Principles,  Sec.  215. 

80.  Hydrodictyon,  the  water  net  (App.  11).  This  type,  which  is  common 
in  some  regions  (as  in  parts  of  the  East  and  Middle  West),  illustrates  excep- 
tionally well  the  features  of  a  cell  colony  and  its  methods  of  reproduction. 
The  cells  in  older  colonies  are  coenocytes,  that  is,  contain  many  nuclei.  They 
have  a  large,  irregular  chromatophore  with  numerous  pyrenoids.  Permanent 
preparations  in  balsam,  stained  with  hsematoxylin  (Sec.  182),  show  these 
points  well.  The  pyreuoids  are  especially  favorable  for  the  study  of  starch 
formation  (see  paper  of  Timberlake,  Annals  of  Botany,  Vol.  XV,  p.  619,  1901). 

Reference.    Goebel,  16,  p.  39 ;  Principles,  Fig.  179. 

81.  Ulothrix,  Draparnaldia,  or  Stigeoclonium.  Ulothrix  is  the  best 
for  the  study  of  zoospore  formation,  but  the  other  types  have  a 
more  complex  and  interesting  morphology. 

A.  Observe  the  attachment  and  appearance  of  the  growth. 

B.  Pick  off  some  filaments  and  moimt  in  water.  Under  l.p. 
study  their  general  morphology.  Are  they  branched  or  un- 
branched  ?  Try  to  find  the  basal  cell  of  a  filament  with  its 
attachment,  holdfast,  and  compare  with  the  cells  in  the  mid- 
dle regions  and  at  the  ends.  Make  outline  sketches  illus- 
trating these  points.  Is  growth  confined  to  the  tips,  or  is  it 
general  throughout  the  filament  ? 

C.  Under  h.p.  study  the  cell  structure.    Note  : 

1.  The  form  of  the  cells,  the  band-like  chromatophore  with 
pyrenoids.    Draw  in  detail. 

2.  Stain  with  iodine  to  bring  out  the  plasma  membrane  and 
nucleus  ;  starch  grains  may  be  observed  around  the  pyre- 
noids. 

D.  Study  the  zoospores  (best  observed  in  the  early  morning 
hours).    In  Ulothrix  note  : 


90  TYPE  STi:i)IES 

1.  That  the  zoospores  are  developed  in  vaiying  numbers  in 
the  cells.  JVIake  counts  and  draw  the  vatious  conditions. 
Certain  striking  peculiarities  of  the  zoospores,  the  pig- 
ment spots  (See  3),  are  easily  recognized  at  this  time. 

2.  The  escape  of  the  zoospores  from  the  parent  cells, 
sporangia,  and  their  swarming  movement  in  the  water. 
They  are  sometimes  called  siuarm  spores. 

3.  The  structure  of  the  zoospore,  showing  pth''^^'*'^^  ^P^^^ 
chromatopliore,  number  and  position  of  the  cilia,  gener- 
ally four  in  number  and  made  clear  when  material  is 
stained  with  iodine  as  described  in  Sec.  67,  B.  Which  is 
the  forward  end  of  the  zoospore  ?    Draw. 

4.  Should  two-ciliate  motile  cells  be  present,  they  may  be 
expected  to  unite,  or  conjugate,  in  pairs  in  the  water, 
showing  that  they  are  sexual  cells,  or  gametes.  The  prod- 
ucts of  the  fusion  are  four-ciliate  cells  with  two  pigment 
spots.    These  are  zygospores,  or  zygotes. 

Because  the  form  or  morphology  of  these  gametes  is  similar, 
this  type  of  sexual  reproduction  is  called  isogamy. 

E.  Note  that  the  zoospores  gather  on  the  illuminated  side  of 
the  vessel  and  settle  down  to  germinate.  After  the  material 
has  been  in  the  vessel  for  three  or  four  days,  observe  the 
growth  of  young  plants,  or  sporelings.  Gather  some  of  the 
sporelings  with  a  pipette  and  draw  a  number  of  stages  illus- 
trating the  germination  of  the  zoospore.  Observe  the  older 
sporelings,  taking  on  the  appearance  of  the  parent  plants,  and 
the  development  from  the  basal  cell  of  a  holdfast. 

E/EFEREXCE.    Piduciples,  Sec.  217. 

Questions.  Describe  as  fully  as  possible  the  life  history  of 
Ulothrix  or  whatever  other  form  may  be  studied.  What 
organisms  do  the  zoospores  resemble  ?  In  what  particulars  ? 
Of  the  two  periods  in  the  life  history,  the  motile  and  quies- 
cent, which  represents  the  more  primitive  condition  of 
plant  life  ?  Which  is  now  the  more  important  for  vegeta- 
tive activities  ?    Which  for  reproductive  ? 


(KD()(iONIUM  91 

82.  Ulva,  the  sea  lettuce.  Follow  in  general  the  outline  for  Ulothrix, 
noting  the  different  morphology  of  the  plant  but  similar  structure  of  the 
individual  cells.  Study  especially  the  margins  of  the  thallus  where  zoospores 
may  be  developed. 

Reference.    Principles^  Sec.  218. 

83.  Cladophora.  Follow  an  outline  similar  to  that  given  for  Ulothrix, 
noting  the  different  morpliology  and  very  different  cell  structure.  The 
older  cells  contain  many  nuclei,  i.e.  are  coenocytes,  and  have  either  a  net- 
like chromatophore  with  pyrenoids,  or  numerous  somewhat  irregular  chlo- 
roplasts.  Permanent  preparations  in  balsam  stained  with  hsematoxylin 
(Sec.  182)  show  these  points  well. 

84.  Zoospores,  their  formation  and  habits.  Use  good  material  of 
Ulothrix,  Drajjanialdia,  Stlgeoclo7umn,  Ulva,  or  Cladophora. 
Place  considerable  fresh  material  in  a  glass  vessel  brightly 
illuminated  on  one  side. 

A.  Zoospores  may  be  developed  the  next  day,  or  perhaps  a  day 
or  so  later.    If  formed,  note  : 

1.  At  what  time  they  appear  in  greatest  quantity  as  a  green 
cloud,  and  in  which  part  of  the  vessel. 

2.  Are  they  developed  in  the  plant  during  the  daytime  ? 
This  will  require  the  examination  of  material  at  various 
times  of  day. 

3.  Can  the  time  of  their  escape  from  the  plant  be  delayed 
by  keeping  material  in  the  dark  ? 

B.  A  full  study  of  the  process  of  zoospore  formation  would 
require  the  killing  and  preservation  of  material  at  intervals 
during  the  night. 

85.  (Edogonium.*  * 

A.  Observe  the  habit  of  the  plant,  the  general  morphology  of 
the  filaments.  Are  they  branched  or  unbranched  ?  Under 
h.p.  draw : 

1.  The  end  of  a  filament  and  some  cells  in  the  middle  region 
crossed  at  one  end  by  delicate  lines,  the  caps.  Note  the 
large  chromatophore  almost  filling  the  cell. 

2.  The  remarkable  disk-like  holdfast  developed  by  the  basal 
cell,  especially  well  shown  in  younger  plants. 


92  TYPE   STUDIES 

B.  Study  fruiting  material  under  h.p.    Draw  : 

1.  The  female  organ,  or  oogonium,  which  is  a  large  swollen 
cell  that  develops  a  single  female  gamete,  the  oosphere, 
or  egg.  Note  the  rounding  off  of  the  Qg%  before  fertiliza- 
tion as  a  naked  protoplast,  and  the  formation  of  a  pore  or 
cleft  to  allow  the  entrance  of  the  sperm. 

2.  The  oospore  within  the  oogonium  developed  from  the 
fertilized  egg,  which  forms  a  heavy  wall  about  itself. 
Observe  the  changed  appearance  of  the  cell  contents,  due 
to  the  presence  of  much  food  material.    Test  for  starch. 

3.  The  male  organs,  or  antheridia,  groups  of  small  disk- 
shaped,  almost  colorless  cells,  each  of  which  develops  two 
sperms.    The  sperms  have  a  circle  of  cilia  at  one  end. 

Because  the  form  or  morphology  of  these  gametes  (eggs  and 
sperms)  is  unlike,  this  type  of  sexual  reproduction  is  called 
heterogamy  (meaning  unlike  gametes). 

C.  The  large  zoospores  may  be  present  in  living  material. 
These  are  formed  singly  in  the  cells.  Note  their  slow  swim- 
ming and  the  circle  of  cilia  at  one  end. 

Should  the  material  of  CEdogonium  be  of  a  species  with  the 
peculiar  dwarf  male  plants,  the  laboratory  directions  would  have 
to  be  considerably  changed. 

Reference  (on  the  formation  of  the  caps).     Goebel,  16,  p.  44. 

Questions.  What  advances  does  (Edogonium  show  over  Ulo- 
thrix  (1)  in  the  structure  of  the  vegetative  cells,  holdfasts, 
and  tip  of  filaments  ?  (2)  in  the  sexual  organs  and  gametes  ? 
Would  the  oospore  from  its  structure  be  expected  to  ger- 
minate at  once,  or  is  it  fitted  to  carry  the  plant  over  unfavor- 
able seasons  ?    Describe  the  life  history  of  (Edogonium. 

86.  Coleochaete  (App.  12).  If  living  material  is  available,  study  its  expanded 
growth  over  the  substratum,  as  illustrated  by  some  of  the  commonest  species. 
Preparations  stained  in  hematoxylin  (Sec.  212)  and  mounted  entire  in  bal- 
sam are  excellent  for  detailed  examination. 

A.  Under  l.p.  note  the  radiate  arrangement  of  the  cells  from  a  center  of 
growth.    Is  the  disk  one  layer  of  cells  thick  or  more  ?    Where  does  cell 


POND  SCUJMS  93 

division  and  growth  take  place  ?  May  the  disk  be  compared  to  a  sys- 
tem of  radiating  and  branching  filaments  adhering  to  one  another  side 
by  side  in  a  plane  ?  Draw  the  outlines  of  several  plants  of  different 
ages,  showing  variety  of  form  and  appearance  of  lobes.  Draw  in  detail 
the  cell  structure  of  a  sector  from  the  center  to  the  margin. 
B.  Search  for  sexual  organs,  oogonia  and  antheridia,  near  the  margins  of 
the  plants  : 

1.  The  oogonia  become  large  cells,  in  most  forms  with  a  delicate  exten- 
sion like  a  long-necked  flask,  and  each  develops  a  single  egg.  The  tip 
of  the  extension  opens,  allowing  the  sperms  to  enter  the  oogonium. 

2.  The  antheridia  are  small,  almost  colorless  cells,  generally  present  in 
small  groups  near  the  margin.    The  sperms  are  two-ciliate. 

3.  After  fertilization  the  egg  forms  a  heavy  wall  about  itself,  thus 
becoming  an  oospore.  Short  filaments  then  develop  from  the  cell 
under  the  oogonium,  and  these  surround  the  oogonium  with  a  cellular 
protective  envelope,  and  the  entire  structure  becomes  a  conspicuous 
fructification. 

87.  Desmids.  Excellent  studies  are  furnished  by  species  of  Closterium. 
(Josmarium.,  Docidium,  Micrasterias.^  etc.,  and  among. the  filamentous  forms 
by  Ilyalotheca,  Desmidium,  etc.  Make  a  general  examination  of  sediment 
from  sunlit  pools,  or  material  skimmed  or  strained  from  the  water,  for  a 
favorable  type. 

A.  Study  the  cell  structure  under  h.p.    Note  and  illustrate  : 

1.  The  symmetrical  halves  of  the  cells  with  the  nucleus  centrally 
placed  between  and  a  chromatophore  in  each  half. 

2.  The  pyrenoids,  generally  conspicuous. 

3.  In  Closterium  a  vacuole  near  each  end  containing  dancing  granules 
(magnesium  sulphate). 

B.  Material  illustrating  the  conjugation  of  desmids  to  form  zygospores? 
is  not  common.    Studies  may  be  made  from  prepared  slides.    Note  : 

1.  That  the  gamete  protoplasts  escape  from  the  parent  cells,  whose 
halves  split  apart,  and  unite  outside  in  the  water  to  form  the  zygo- 
spore or  zygote. 

2.  That  the  zygospore  has  a  heavy  protective  wall  elaborately  marked 
in  some  species. 

88.  Pond  scums.*  *  An  outline  for  the  study  of  Spirogijra  is 
given  in  Sees.  56,  57,  61.  Similar  studies  may  be  planned  for 
Zygneina  and  Mouyeotia,  which  differ  from  Spirogyra  and  from 
one  another  chiefly  in  the  form  of  the  chromatophores  and  the 
X)Osition  of  the  zygospores  between  the  conjugating  cells. 


94  TYPE  STUDIES 

89.  Diatoms.  Good  material  is  generally  present  in  sediment  from  sunlit 
pools  such  as  will  furnish  desmid  material.  Brown  scums  or  brown  slimy 
coatings  are  frequently  almost  pure  growths  of  diatoms.  Make  a  general 
examination  of  material  and  note  especially  stalked  forms  and  those  united 
into  filaments  or  chains.  Search  especially  for  large,  boat-shaped  types 
(generally  Pinnularia  or  Navicula)  that  move  to  and  fro  in  the  water.  Study 
the  cell  structure  of  these  latter  forms  under  h.p.    Draw  : 

A.  An  upper  or  valve  view  (elliptical  in  outline)  which  shows  a  suture, 
raphe,  running  almost  the  entire  length  of  the  cell,  and  a  nodule  at 
either  end  and  in  the  middle  region.  Two  brown  chromatophores  lie 
along  either  side  of  the  cell  and  the  nucleus  in  the  center.  Note  the 
globules  of  oil  in  the  cell.  Draw  an  outline  on  a  large  scale,  showing 
the  markings  on  the  siliceous  shell. 

B.  A  side  or  girdle  view  (rectangular  in  outline)  which  in  a  large  cell 
will  show  at  the  ends  an  overlapping  of  the  two  siliceous  shells, 
inclosing  the  protoplast,  which  fit  together  as  a  cover  fits  over  a  box. 
Illustrate  these  points  and  also  the  position  of  the  chromatophores, 
oil  globules,  and  nucleus. 

C.  Examine  some  of  the  polishing  powders,  such  as  electro-silicon,  for 
diatoms,  making  mounts  in  water  or  balsam  (App.  13). 

90.  Vaucheria,  the  green  felt.**  Some  species  are  terrestrial, 
growing  on  damp  earth  and  common  in  flowerpots  in  greenhouses. 
Others  are  aquatic,  forming  heavy,  dark  green  mats  on  the  bot- 
tom of  muddy  pools  and  ditches.  Examine  the  felted  growth^ 
its  coarseness,  feeling,  size  of  filaments,  irregular  branching.  Do 
the  positions  of  the  filaments  bear  any  relation  to  the  direction 
of  light? 

A.  Carefully  mount  some  filaments  in  water.  Draw  under 
m.p.  Is  the  diameter  of  the  filament  the  same  throughout 
any  considerable  length?  Are  cross  walls  present?  Is  the 
protoplasm  uniformly  green?  Colorless,  root-like  branches, 
rhizoids,  may  be  found.     Under  h.p.  draw : 

1.  The  end  of  a  filament,  showing  the  arrangement  of  the 
protoplasm,  the  cell  wall,  the  numerous  chloroplasts  and 
glistening  globules  of  oil,  the  position  of  a  central  vacuole 
running  leiigthwise  of  the  filament. 

2.  Under  the  highest  magnification  draw  stages  in  the  multi- 
plication of  the  chloroplasts. 


VAUCHERIA  95 

3.  Stain  with  iodine.    Is  starch  present  ? 

4.  Material  stained  with  hsematoxylin  and  mounted  in  balsam  will 
show  the  very  numerous  minute  nuclei.  The  filaments  are  there- 
fore cop.nocytes  (see  Principles,  Sec.  229). 

B.  In  fruiting  material  study  and  draw  the  sexual  organs,  vari- 
ously grouped  in  different  species. 

1.  The  large  oval,  female  organ,  or  oogonium,  sessile  on  the 
parent  filament  but  separated  from  it  by  a  wall.  The  pro- 
toplast becomes  a  naked  egg  within  the  oogonium,  which 
forms  a^:>o/'e  (for  the  entrance  of  sperms)  in  a  short,  beak- 
like structure  somewhat  at  one  side  near  the  tip. 

2.  The  mature  oosjjore,  with  its  heavy  wall,  developed  from 
the  fertilized  egg.  Note  the  changed  appearance  of  the  con- 
tents of  the  oospore,  now  rich  in  food  material. 

3.  The  male  organ,  or  antliev'idium,  at  the  end  of  a  short 
branch  bent  like  a  crook,  and  separated  by  a  wall  from 
the  parent  filament.  It  develops  a  very  large  number  of 
minute  two-ciliate  sperms. 

Because  the  form  or  morphology  of  these  gametes  is  unlike, 
this  type  of  sexual  reproduction  is  called  heterogamy. 

C.  Allow  material  to  remain  in  a  vessel  of  water.    It  may  form 
zoospores}    If  so,  note  : 

1.  Their  large  size  and  habits  of  germination.  If  studied 
when  motile,  observe  their  slow  swimming.  Stain  the  zoo- 
spores with  iodine  to  show  the  very  numerous  delicate  eilia 
all  over  the  surface ;  these  are  really  pairs  of  cilia,  each 
pair  above  a  nucleus  (see  PrincqAes,  Fig.  189,  C).    Draw. 

2.  The  formation  of  the  zoospores  at  the  tips  of  filaments 
which  appear  darker  in  color.  Note  the  cross  wall  cutting 
off  a  terminal  sp)orangium,  the  protoplasm  of  which  becomes 
the  single  zoospore.     Draw. 

3.  Stages  in  the  germination  of  the  zoospore  and  the  devel- 
opment of  the  sporelings. 

1  Mateiial  of  Vaucherla  is  likely  to  produce  zoospores  in  large  numbers  if  placed 
in  fresh  water  after  some  days  of  cultivation  in  live  per  cent  Knop's  solution 

(Sec.  L'OO,  A). 


96  TYPE   STUDIES 

Questions.  How  would  you  distinguish  aquatic  species  of 
Vaucheria  in  the  field  from  Spirog[/ra  ?  from  (Edogonium  ? 
Describe  the  protoplasmic  structure  of  the  filaments.  What 
are  the  characteristics  of  a  coenocyte  ?  Do  the  nuclei  occupy 
fixed  positions  in  the  filament  ?  Where  in  the  filam^ent  does 
growth  in  length  take  place  ?  Compare  the  structure  of  the 
ccenocytic  zoospore  of  Vaucheria  with  the  protoplasmic 
contents  of  a  sporangium  of  such  a  tj^pe  as  Cladophora  (see 
Princijdes,  Fig.  184,  B)  or  the  water  molds  (see  Principles, 
Fig.  214,  C)  and  show  the  points  of  resemblance.  What 
difference  in  the  behavior  of  the  protoplasm  results  in  the 
formation  of  a  single  zoospore  in  Vaucheria  and  of  many 
zoospores  in  the  other  forms?  What  takes  the  place  of 
starch  in  Vaucheria  ?  Would  the  oospore  from  its  structure 
be  expected  to  germinate  at  once  ?  Describe  the  life  history 
of  Vaucheria. 

91.  Chara  or  Nitella,  stoneworts.  Examine  the  growth  habits  of  the  plant. 
Is  the  surface  incrusted  with  lime  ?  Study  the  general  morphology,  noting 
the  well-defined  stems,  the  circles  of  lateral,  leaf -like  hranchlets,  the  joints  or 
nodes  separated  by  internodes,  the  growth  from  a  bud-like  tij).  Are  these 
characters  which  would  be  expected  of  a  thallophyte  ?  Is  the  structure  a 
thallus  ?    Sketch  these  features  of  the  general  morphology. 

A.  In  fruiting  material,  either  living  or  preserved,  note  the  position  of 
the  sexual  organs,  generally  in  pairs,  an  antheridium  and  an  oogonium. 
If  the  antheridium  is  above  the  oogonium,  the  form  is  Nitella;  if 
below,  Chara.  Material  heavily  incrusted  with  lime  may  be  treated 
with  1  per  cent  chrom-acetic  acid,  which  will  dissolve  it  away.  Draw 
a  group  of  sexual  organs,  shoAving  : 

1.  For  the  oogonium,  the  circle  of  five  spirally  \no\x\\(\.  filaments,  adher- 
ing to  one  another  side  by  side,  which  envelop  the  egg,  the  tips  of 
the  filaments  projecting  beyond  the  es:g  as  the  crown.  If  there 
are  five  cells  in  the  crown,  the  form  is  Chara;  if  two  tiers  of  five 
cells  each,  the  form  is  Nitella. 

2.  For  the  antheridium  the  surface  view  of  large,  triangular,  flattened 
cells,  called  shields  (eight  in  all),  composing  the  outer  envelope. 

B.  Crush  the  antheridium,  noting  the  numerous  coiled  antheridial  fila- 
ments, composed  of  disk-shaped  cells,  each  of  which  develops  a  sperm. 
The  attachment  of  the  antheridial  filaments  by  means  of  a  series  of 


ECTOCARPUS  97 

cells  to  the  shields  is  difficult  to  determine,  and  is  best  omitted  in  a 
general  study. 

C.  Crush  old  oogonia  containing  thick-walled  oospores  and  note  the  cell 
contents  full  of  food  material.    Test  its  nature  with  iodine. 

D.  Should  the  material  be  a  species  free  from  lime  (especially  in  the  case 
of  Nitella)  and  one  whose  internodal  cell  is  not  covered  by  corticating 
filaments,  study  the  circulation  of  protoplasm  in  the  internodal  cell  as 
described  in  Sec.  64,  B. 

E.  A  detailed  histological  examination  of  a  stonewort  is  full  of  interest, 
but  rather  special  for  a  general  course.  Its  full  understanding  demands 
a  study  of  microtome  sections  of  the  growing  points,  to  establish  the 
remarkable  method  of  growth,  which  can  be  followed  throughout  the 
branchlets  and  corticating  filaments  that  grow  over  the  internodes 
in  many  species.  The  method  of  growth  furnishes  the  key  to  the 
detailed  morphology  of  the  stoneworts. 

Hefekence.    Goebel,  16,  p.  52. 


THE  BKOWN  ALGJE,  OR  PH^OPHYCE^: 

92.  Field  work  on  the  marine  algae.  Study  when  possible  the  distribution 
of  marine  algse  on  rocks  at  the  seaside.  Describe  the  conspicuous  growths 
in  three  zones  :  (1)  those  well  above  low-tide  mark  ;  (2)  those  at  low-tide  mark  ; 
and  (3)  those  below  low -tide  mark.  AVhere  are  the  sea  lettuces  most  numer- 
ous ?  the  rockweeds  ?  the  kelps  ?  the  larger  red  algpe  ?  Examine  sunlit  tide 
pools  and  compare  with  very  shaded  pools.  If  sheltered  bays  can  be  studied, 
note  the  character  of  the  forms  on  stones  in  shallow  water,  and  on  the  eelgrass. 
If  salt  marshes  can  be  examined,  study  the  algal  flora  along  the  margins  of 
the  tidal  streams  and  in  the  pools.  Make  collections  of  the  conspicuous 
forms,  noting  their  habitats,  and  bring  to  the  laboratory  for  examination. 

93.  Ectocarpus.  Examine  the  habit  of  the  plant,  tufted  growth,  attach- 
ment. 

A.  Draw  a  portion  under  m.p.  to  show  the  branching.  Are  the  tips  of 
the  filaments  all  alike  in  structure  ?  Try  to  determine  the  method  of 
growth  when  they  end  in  hairs.  Draw  a  cell  under  h.p.,  showing  the 
irregular  chromatophore. 

B.  In  fruiting  material  find  either  or  both  of  the  two  forms  of  sporangia. 
Draw  under  h.p  : 

1.  Unilocular  sporangia,  single,  cells,  solitary,  sessile,  or  on  short  stalks 
in  some  species  and  in  chains  in  others,  as  in  Pylaiella  (Ectocarpus) 
Uttoralis.  Each  sporangium  develops  a  large  number  of  two-ciliate 
zoospores. 


r 


98  TYPE  STUDIES 

2.  Plurilocular  sporangia  or  gametangia.  These  are  branches  composed 
of  a  very  large  number  of  small  cubical  cells,  each  of  which  produces 
one  or  perhaps  two  or  three  two-ciliate  elements  similar  to  zoospores, 
but  which  are  known  to  be  gametes  in  some  forms,  conjugating  in 
pairs  as  in  Ulothrix.  Trace  the  development  of  the  plurilocular 
sporangia  from  vegetative  branches.  It  should  be  noted  that  they 
are  many-celled  organs  both  in  structure  and  origin. 

3.  Should  zoospores  or  gametes  be  discharged  from  living  material, 
study  their  movements  and  then  stain  with  iodine  (as  described  in 
Sec.  67,  B).  Note  their  kidney  form  and  the  pair  of  cilia  inserted 
laterally. 

94.  Kelps.  Study  the  morphology  of  such  kelps  as  may  be  available,  not- 
ing holdfast,  stalk,  and  blade.  Should  the  blades  be  in  fruit,  cut  sections  in 
pith  to  show  the  one-celled  sporangia. 

95.  Fucus,  the  rockweed."*  *  Fucus  vesiculosus  is  perhaps  the 
most  convenient  species  for  study.  Describe  its  color,  consist- 
ency, and  life  habits  if  studied  living  on  the  rocks. 

A.  Make  a  habit  sketch  of  a  plant,  noting: 

1.  Its  method  of  branching,  thickened  midrib,  and  lateral 
expanded  margin. 

2.  The  presence  of  air  bladders  and  swollen  tips,  called 
receptacles. 

3.  Sunken  regions  in  the  receptacles,  termed  conceptacles, 
each  opening  to  the  exterior  by  a  2^0  re  through  which 
protrudes  a  cluster  of  delicate  filaments,  paraphijses. 

4.  The  flattened  vegetative  tips  with  a  jrit  at  the  end,  at  the 
bottom  of  which  lies  a  group  of  cells  forming  the  group- 
ing point. 

5.  The  disk-shaped  holdfast. 

B.  Cut  across  a  receptacle  and  under  l.p.  or  with  a  hand  lens 
diagram  the  distribution  of  the  conceptacles.  Note  in  living 
material  the  color  of  the  contents  of  the  conceptacle,  whether 
dark  green  or  orange,  and  later  determine  which  contain 
male  organs  and  which  female. 

C.  Dig  out  with  the  point  of  a  scalpel  the  contents  of  a  con- 
ceptacle,  and  mount  in  water.     Study  the  sexual  organs. 


FUCUS  99 

Does  a  plant  of  Fiiciis  vesiculosus  have  both  sexual  organs 
in  the  same  conceptacle  ?  on  the  same  plant?    Draw: 

1.  The  female  organs,  oogonia,  large  cells  which  develop 
eight  eggs  each. 

2.  The  male  organs,  antheridia,  small  cells  generally  borne 
in  clusters  on  stalks.  Each  develops  numerous  (over  one 
hundred)  sperms. 

Because  of  the  extreme  differentiation  of  the  eggs  and  sperms 
the  condition  in  Fucus  is  one  of  the  highest  expressions  of  het- 
erogamy. 

A  plant  is  called  diwcious  when  the  sexual  organs  are  borne  on 
different  individuals,  vioncecious  if  both  organs  are  on  the  same 
individual. 

D.  Cut  thin  sections  in  jDith  or  study  stained  microtome  sections  of  recep- 
tacles (Sec.  212)  and  draw  on  a  large  scale  the  outline  of  a  conceptacle, 
showing  the  opening  with  protruding  filaments,  paraphyses,  the  lining 
membrane  with  the  sexual  organs  in  position,  the  network  of  filaments 
within  the  receptacle. 

E.  Living  male  and  female  plants  may  be  separated,  rolled  up  in  paper, 
and  kept  in  a  tight  box.  The  contents  of  ripe  conceptacles  will  then 
ooze  out  from  the  openings.  When  such  contents  are  placed  in  sea 
water  the  slime  dissolves  and  the  gametes,  eggs  or  sperms,  are  set  free. 
If  mixed  together  the  sperms  at  once  swarm  around  the  eggs  and  the 
conditions  under  which  fertilization  takes  place  may  be  observed 
under  the  microscope.  Note  the  rotation  of  the  eggs,  set  in  motion  by 
the  swarming  of  the  sperms.  Sketch  the  appearance  of  the  eggs.  Stain 
with  iodine  and  draw  the  sperms  under  the  highest  magnification. 

F.  Fertilized  eggs  if  placed  in  sea  water  in  a  covered  watch  glass  will 
germinate,  developing  into  sporelings.    Draw  stages. 

Questions.  Where  do  the  rockweeds  grow?  How  can  they 
withstand  the  beating  of  surf  on  the  rocks  ?  Would  the 
vegetative  body  of  a  rockweed  be  called  a  thallus  ?  Why  ? 
Of  what  service  are  the  air  bladders  ?  Where  does  fertiliza- 
tion take  place  in  nature.  How  might  the  gametes  escape 
from  the  conceptacles  ?  Why  is  it  not  necessary  for  an 
egg  to  become  a  resting  spore  (oospore)  in  a  marine  alga  ? 
Describe  the  life  history  of  Fucus. 


100  TYPE   STUDIES 

96.  Sargassum.  Study  the  general  morpliolugy  of  Sargassum  from  dried 
specimens  on  herbarium  sheets.  Note  the  stem,  leaf-like  lateral  structures, 
branching  receptacles,  stalked  berry-like  air  bladders,  and  holdfast.  Illustrate 
these  features.    Is  this  structure  a  thallus  ? 

THE   RED   ALG^,   OK   RHODOPHYCE^ 

97.  Nemalion.  Note  the  form  and  consistency  of  the  thallus. 
The  color,  which  may  be  observed  from  herbarium  material,  is 
not  typical  of  the  red  algse. 

A.  Crush  out  a  tip  under  the  cover  glass.  Under  m.p.  study 
the  vegetative  structure  composed  of  filaments  held  together 
by  a  gelatinous  substance. 

1.  Diagram  the  form  and  arrangement  of  the  filaments  in 
the  interior  and  outer  regions. 

2.  Draw  details  of  the  vegetative  cells  under  h.p.,  showing 
the  peculiar  chromatophores  and  the  attachment  of  the  pro- 
toplasts to  one  another  by  delicate  strands  of  protoplasm. 

B.  From  a  crushed-out  tip  of  a  male,  or  antheridial,  plant  study 
the  clusters  of  sperm  mother  cells  forming  antheridia  at  the 
tips  of  the  filaments.  Draw.  Each  sperm  mother  cell  devel- 
ops a  single  non-motile  sperm. 

C.  From  a  crushed-out  tip  of  a  female,  or  cystocarplc,  plant 
study  and  draw  : 

1.  The  large,  mature,  globular  fructification  called  a  cysto- 
carp.  The  development  of  its  spores,  cavpospores,  at  the 
tips  of  filaments. 

2.  Earlier  conditions.  Search  for  the  female  orgain  from 
which  the  cystocarp  is  developed.  The  female  organ  is  a 
single  cell,  carpoyonium,  corresponding  to  an  oogoniutti.  It 
is  situated  at  the  end  of  a  short  branch,  and  bears  a  deHfeate 
extension,  the  trichogyne,  an  organ  for  the  reception  of  the 
non-motile  sp)erms.  Draw  a  carpogonium  with  trichogyne, 
probably  having  one  or  more  sperms  attached,  or  some  early 
stage  in  the  development  of  the  cystocarp  when  the  fer- 
tilized carpogonium  may  be  divided  into  several  cells. 


1M)LYSIPH0NTA  101 

3.   Follow  the  history  of  the  trichogyne  through  later  stages 
in  the  development  of  the  cystocarp.    Trace  the  develop- 
ment of  the  filaments  composing  the  cystocarp. 
Reference.    Principles,  Sec.  243. 

Questions.  What  part  of  the  protoplasm  in  the  female  organ 
corresponds  to  an  egg  ?  Is  the  structure  produced  by  the 
fertilized  Qg^  a  new  form  of  development  in  your  study  of 
the  algse  ?  What  is  its  relation  to  the  sexual  plants  ? 
Describe  the  life  history  and  construct  a  formula  expressing 
the  relationships  of  the  different  phases  (App.  18). 

98.  Batrachospermum.  This  fresh-water  type  of  the  Rhodophyceoe  is  an 
excellent  substitute  for  Nemalion.  Follow  a  similar  outline  of  study,  noting 
its  peculiarities  of  habit,  color,  the  preliminary  growth,  Chantransia,  if 
present,  etc. 

99.  Polysiphonia.  From  herbarium  specimens  examine  the  general  growth 
habits,  method  of  branching,  attachment,  and  color.  Note  that  there  are 
different  forms  of  plants,  characterized  by  different  types  of  reproductive 
organs.    It  is  simplest  to  begin  the  study  with  the  asexual  or  tetrasporic  plant. 

A.  The  vegetative  structure  may  be  studied  from  any  form  of  the  plant. 
Mount  a  few  filaments.     Note  under  h.p. :  ^ 

1.  That  the  filaments  are  composed  of  rows  of  cells,  called  siphons, 
placed  end  to  end  and  connected  with  one  another  by  delicate  strands 
of  protoplasm  ;  that  the  cells  contain  disk-shaped  chromoplasts.  Count 
the  siphons,  if  possible,  by  focusing  up  and  down.  Draw  part  of 
a  filament. 

2.  That  the  tip  of  the  filament  bears  clusters  of  hairs  and  that  it  ends 
in  a  single  cell,  the  apical  cell. 

3.  Crush  the  filaments  or  cut  sections  and  note  that  there  is  a  central 
siphon  surrounded  by  peripheral  siphons.  Diagram  their  number 
and  arrangement  as  they  would  appear  in  cross  section. 

B.  The  asexual  or  tetrasporic  plant.  Mount  filaments  bearing  tetraspores. 
Draw  : 

1.  Part  of  a  branch  under  m.p.,  showing?  position  of  tetraspores. 

2.  A  group,  or  tetrad,  of  four  mature  tetraspores  surrounded  by  the 
peripheral  siphons.  Note  that  the  spores  are  contained  in  a  mother 
cell. 

3.  Trace  if  possible  the  development  of  the  tetraspore  mother  cell,  deter- 
mining its  origin  from  the  central  siphon  and  final  attachment  to  the 
latter  through  a  stalk  cell. 


102  TYPE  STUDIES 

C.  The  male  or  anthcridial  plant. 

1.  Sketch  ill  outline  the  position  of  the  male  organs,  or  antheridia,  in 
chisters  at  the  tips  of  the  tilaments. 

2.  Draw  the  outline  of  an  antheridium  on  a  large  scale  and  fill  in  the 
details  of  a  portion  showing  the  outer  layer  of  small,  colorless  cells 
which  develop  the  sperms. 

3.  Crush  an  antheridium  and  try  to  determine  its  general  plan  of  struc- 
ture. There  is  a  central  siphon  surrounded  by  a  densely  branching 
system  of  small  cells  ending  in  the  sperms  at  the  peripheiy.  Diagram 
the  relation  of  these  parts.  Trace  the  development  of  the  antherid- 
ium.   It  should  be  clear  that  the  organ  is  a  modified  branch. 

D.  The  female  or  cystocarpic  plant. 

1.  The  fructification,  called  a  cystocarp,  is  in  Polysiphonia  an  urn- 
shaped  structure  in  which  a  cluster  of  carpospures  is  developed  from 
a  large  cell  at  the  base.  Draw  a  mature  cystocarp  and  afterwards 
crush  out  the  pear-shaped  carpospores. 

2.  Examine  younger  cystocarps,  tracing  the  structures  back  to  the 
female  organ,  or  procarp.  The  procarp  is  a  modified  branch  and 
many  celled.  The  carpogonium  is  enveloped  by  sterile  cells,  from 
among  which  the  trichogyne  projects  somewhat  at  one  side. 

The  development  of  the  cystocarp  is  too  difficult  a  subject  for  general 
study.  It  has  recently  been  traced  by  Yamanouchi  {Botanical  Gazette^ 
Vol.  XLII,  p.  401,  1906),  who  has  established  an  alternation  of 
tetrasporic  plants  with  the  sexual.  The  former,  together  with  certain 
developments  from  the  carpogonium  leading  to  the  production  of  the 
carpospores,  constitute  an  asexual  or  sporophytic  phase  in  the  life 
history.  The  sexual  plants  are  gametophytes  and  the  sporophyte 
generation  begins  with  the  fertilized  carpogonium  and  ends  with 
the  formation  of  the  tetraspores,  thus  including  the  spore-produc- 
ing tissues  of  the  cystocarp,  together  with  the  tetrasporic  plant  (see 
Principles,  Sees.  245,  246). 


THE  BACTERIA,  OR   SCHIZOMYCETES 

100.  The  culture  of  bacteria  on  potato**  (App.  14). 
A.  Preparation  of  the  culture  surface. 

1.  Select  medium-sized,  sound  potatoes,  and  boil  with  the 
skins  on  for  fifteen  minutes,  —  not  so  long  that  they 
will  not  readily  hold  their  form  when  cut. 

2.  While  the  potatoes  are  cooking,  boil  six  Petri  dishes  in 
clear  water  for  fifteen  minutes.    Lift  the  Petri  dishes  out 


BACTERIA  103 

carefully  by  the  edge,  drain  off  most  of  the  water,  but  do 
not  wipei  Lay  a  piece  of  round  filter  paper  in  the  bottom  of 
each  dish,  placing  the  cover  over  it  at  once.  It  is  better  that 
the  paper  be  sterilized  by  heating  in  a  hot-air  chamber  at 
a  temperature  of  150°  C.  for  half  an  hour,  but  this  is  not 
necessary  if  a  good  quality  of  filter  paper  be  used.  There 
have  now  been  prepared  six  moist  chambers,  relatively 
free  from  germs.    Why  ? 

3.  Cut  the  boiled  potatoes  into  thin  slices  with  a  knife 
that  has  been  thoroughly  cleaned  and  heated  in  a  flame. 
Place  a  slice  or  two  on  the  filter  paper  in  each  Petri  dish. 
Be  careful  not  to  touch  the  cut  surface  with  the  fingers  or 
any  object  save  the  heated  knife  blade.  Lift  the  cover  of 
the  Petri  dish  carefully,  handling  only  the  outer  edge,  and 
replace  quickly.  The  culture  surface  is  now  ready  for  inoc- 
ulation. The  boiling  of  the  starch  prepares  a  much  better 
culture  medium  than  the  surface  of  a  raw  potato. 
B.  Inoculation  of  the  culture  surface.    Care  should  be  taken  to 

lift  off  the  covers  of  Petri  dishes  gently,  and  replace  at  once 

after  inoculation. 

1,  2.  Lift  the  covers  from  two  dishes  and  expose  the  potato 
to  the  air  for  five  minutes  where  it  is  likely  to  gather  parti- 
cles of  dust.  Place  one  dish  in  a  cool  situation  (as  an  ice 
box),  and  the  other  in  a  warm  one  (as  near  a  radiator), 
noting  the  temperatures  with  a  thermometer. 

3.  Draw  the  finger  nail  twice  across  the  cut  surface  of  a 
potato  in  another  dish,  in  two  parallel  lines  half  an  inch 
apart. 

4.  Wash  the  edge  of  a  public  drinking  cup  or  the  outlet 
of  a  faucet  with  a  cupful  of  distilled  or  sterilized  water. 
Place  a  drop  of  the  water  on  the  surface  of  the  fourth 
slice,  noting  its  position. 

5.  Spread  a  very  small  quantity  of  milk  over  the  surface  of 
another  potato  with  the  sterilized  point  of  a  knife. 

6.  Leave  the  sixth  potato  slice  untouched  for  comparison 
with  the  inoculated  ones. 


104  TYPE   STUDIES 

C.  Label  each  potato  culture  with  a  number  and  write  an 
account  of  each,  giving  (1)  day  and  hour  of  inoculation,  and 
(2)  method.  Examine  the  cultures  for  several  successive 
days  and  record  the  changes  from  day  to  day.  Describe  and 
sketch  the  appearance  of  the  growths,  their  color,  form, 
and  consistency. 

101.  Fluid  cultures  of  bacteria.*  * 

A.  Hai/  Infusion.  Place  some  hay  in  a  small  quantity  of  water 
and  leave  in  a  warm  place  for  a  few  days.  The  scum  that 
forms  is  principally  bacterial  and  composed  largely  oi  Bacillus 
subtil  is.  Later  quantities  of  infusoria,  chiefly  Paramoecium, 
will  develop. 

B.  Mother  of  vinegar.  Examine  the  brownish  mass  called  mother  of  vine- 
gar from  a  vinegar  jar  or  bottle.  This  mass  is  a  good  illustration 
of  what  is  called  a  zoogloea,  —  that  is,  a  gelatinous  growth  developed 
by  bacteria. 

C.  Decaying  algoe.  Allow  algse,  such  as  Vaucheria  or  Spirogyra,  to  decay 
in  a  bottle  in  a  warm  place.  A  bacterial  scum  will  form  that  generally 
contains  quantities  of  the  spiral  filamentous  type,  SpirochcBte.  Spiro- 
chcete  will  also  generally  develop  in  filtered  bean  or  pea  broth  made 
by  boiling  crushed  beans  or  peas.     Xote  the  putrid  odor. 

102.  Microscopical  studies  of  bacteria. 

A.  Examine  under  h. p.  the  scum  from  a  hay  infusion  (Sec.  101,  A) 
for  the  hay  bacillus.  Bacillus  subtllis.    Note  : 

1.  Colorless  rod-shaped  cells,  solitary  or  forming  filaments 
of  various  lengths,  their  movement  in  the  water,  and  their 
size  as  compared  with  such  infusoria  as  may  be  present, 
particularly  ParaTn^oBciunn.    Draw. 

2.  Study  under  veiy  high  magnification,  if  desired,  the  crosswise 
division,  or  fission,  of  the  rods.  This  study  will  demand  an  immer- 
sion lens. 

.3.  Place  some  of  the  scum  in  distilled  water  and  after  several  days, 
when  the  food  supply  has  become  exhausted,  study  under  an  immer- 
sion lens  the  small,  thick-walled  spores  formed  within  the  rods. 

4.  Other  bacteria  will  probably  be  present  besides  the  hay  bacillus. 
Search  for  spherical  types,  Micrococcus,  and  filamentous  forms,  the 
latter  sometimes  spirally  twisted  and  motile.  Spirillum  or  Spirochcete. 


YEAST  105 

B.  Mount  a  small  quantity  of  the  "■  fur  '^  from  the  teeth  fipread 
out  in  a  drop  of  water.     A  number  of  forms  will  be  found* 
(Strasburger-Hillhouse,  Fig.  102). 

C  .  Study  preparations  from  some  of  the  brightly  colored  colonies  (red, 
yellow,  pink,  etc.)  which  may  develop  on  the  potato  cultures,  gener- 
ally composed  of  very  minute  forms. 

D.  Examine  mother  of  vinegar  (Sec.  101,  B)  for  small  rod-shaped  types 
{Bacillus  aceti,  with  other  forms). 

E.  Study  the  growths  from  the  infusion  of  decaying  algae  (Sec.  101,  C) 
for  long,  spirally  twisted  filaments  of  Spirochcete  in  very  active  move- 
ment. 

103.  Staining  of  bacteria.  Stained  preparations  of  bacteria  frequently 
show  much  more  clearly  tharn  the  living  forms  the  structure  of  the  cells  and 
processes  of  spore  formation.  The  demonstration  of  cilia  requires  very 
high  powers  and  special  methods. 

A.  Mix  a  minute  quantity  of  bacterial  slime  {Bacillus  subtilis  is  a  good 
form)  in  a  watch  glass  of  water.  Spread  a  film  of  the  water  on  a  cover 
glass  and  allow  it  to  dry.  The  process  may  be  hastened  by  holding 
the  cover  glass,  film  side  up,  well  above  a  fiame  ;  the  heat  helps  to 
attach  the  bacteria  to  the  cover  glass. 

B.  Dip  the  cover  glass  in  a  strong  water  solution  of  fuchsin  or  of  gentian 
violet.  Rinse  off  the  stain  in  water  and  examine  to  see  if  the  bacteria 
are  overstained.  If  so,  extract  the  stain  with  alchohol.  Finally  allow 
the  cover  glass  to  dry  and  mount  in  Canada  balsam. 

Questions.  What  types  of  the  algse  do  the  bacteria  most 
resemble  in  their  cell  structure  and  morphology  ?  How  do 
the  bacteria  obtain  their  food  and  what  is  its  character  ? 
What  changes  have  you  observed  produced  by  growths  of 
bacteria  ? 

THE   YEASTS,   OR   SACCHAEOMYCETES 

104.  The  culture  of  yeast.*  *  Prepare  a  pint  of  a  five  or  ten  per 
cent  solution  of  molasses  in  water. 

A.  Place  a  small  quantity  of  the  solution  in  a  test  tube  and 
add  a  fragment  of  fresh  yeast.  The  scum,  or  sediment,  after 
twenty-four  hours  will  give  excellent  material  of  growing 
yeast  for  microscopical  study. 


106  TYPE   STUDIES 

B.  Shake  half  a  yeast  cake  in  a  pint  of  molasses  solution  and 
place  in  a  bottle  inverted  over  a  dish  of  water.  Note  the 
fermentation  indicated  by  the  formation  for  several  days  of 
bubbles  of  gas,  which  will  collect  in  the  upper  jegion  of 
the  inverted  bottle.  Test  the  nature  of  this  gas  by  the  aid 
of  limewater  in  the  manner  described  in  Exp.  lY.  What  is 
the  gas  ?  Note  the  decided  odor  of  alcohol  in  the  fluid  after 
fermentation  has  ended. 

C.  If  convenient  distill  off  about  a  quarter  of  the  fermented  liquid,  add 
a  little  quicklime  to  the  distillate,  and  redistill  into  a  carefully  cooled 
receiver.  Pour  some  of  the  second  distillate  into  a  saucer,  note  its 
odor,  and  try  to  light  it. 

105.  Structure  of  the  yeast  cell.*  * 

A.  Mount  in  water  some  of  the  scum,  or  sediment,  present  in 
the  culture  described  in  Sec.  104,  A.  Brewer's  yeast,  if 
obtainable,  is  perhaps  the  best  form  for  microscopical  study, 
especially  the  ''  top  yeast."  Observe  the  colorless  oval  cells 
frequently  occurring  in  short  chains  or  small  groups.  These 
are  yeast  cells.    Make  drawings  to  show  : 

1.  A  large  cell  with  granular  protoplasm  containing  one  or 
more  vacuoles. 

2.  The  formation  of  new  cells  by  the  process  of  budding. 
Draw  stages  in  the  development  and  growth  of  the  buds, 
and  the  formation  of  chains  or  clusters  of  cells. 

B.  Mount  a  bit  of  yeast  cake  in  water.    Stain  with  iodine. 

1.  What  are  the  large  grains  composing  the  bulk  of  the 
yeast  cake  ? 

2.  What  is  the  staining  reaction  of  the  yeast  cell  with 
iodine  ?    Is  there  starch  in  the  cell  ? 

Questions.  What  are  the  life  habits  of  the  yeast  plant  ? 
What  is  its  food  and  how  do  the  cells  obtain  it  ?  Can  the 
yeast  cell  absorb  solid  food  like  an  Amoeba  ?  Why  ?  What 
happens  during  the  process  of  fermentation  ?  What  part 
does  yeast  play  in  the  raising  of  bread  ?  What  substitutes 
for  yeast  may  be  employed  in  bread  making,  and  why? 


Riirzoprs  107 

THE  ALGA-LIKE    FUNGI,   OR   PHYCOMYCETES 

106.  Rhizopus  nigricans  (Mucor  stolonifer),  the  bread  mold** 
(App.  15).  A  culture  is  easily  obtained  by  placing- a  slice  of 
bread  on  a  rack,  or  other  support,  inside  a  bell  jar  set  in  a  dish 
of  water  to  form  a  moist  chamber. 

A.  Note  the  gradual  development  of  mold  over  the  substratum 
(bread),  and  the  color  and  size  of  the  filaments,  or  hypluv^ 
which  together  constitute  the  mycelium.  Is  the  mycelium 
all  above  the  surface  of  the  bread  ?  Observe  the  develop- 
ment of  upright  stalks,  in  groups,  and  the  black  sporangia 
formed  at  their  ends.  Is  the  direction  of  the  growth  of  the 
hyph«  above  the  surface  of  the  bread  influenced  by  light  ? 

B.  Lift  off  carefully  some  of  the  mycelium  and  mount  in 
water.  Note  under  m.p.  the  color  and  structure  of  a  hypha. 
Is  it  septate  ?  What  alga  does  it  resemble  in  cell  structure 
except  for  the  absence  of  chloroplasts  ?  Draw  under  h.p. 
a  tip  showing  the  cell  wall  and  distribution  of  the  proto- 
plasm. Observe  the  glistening  globules  of  oil  or  fat,  and 
watch  for  streaming  movements.  Material  stained  with 
hsematoxylin  (Sec.  182)  will  demonstrate  the  very  numerous 
minute  nuclei.     Is  the  filament  a  coenocyte  ? 

C.  Mount  portions  of  the  mycelium  with  groups  of  stalks 
bearing  sporangia  (sporangiophores).  Draw  a  group  of  stalks 
about  five  times  its  natural  size.    Note  and  draw  under  m.p. : 

1.  The  base  of  a  group,  showing  a  cluster  of  root-like  fila- 
ments, rhizoids,  that  penetrate  the  substratum.  ' 

2.  Stages  in  the  development  of  the  sjiorangium,  showing 
0^)  the  enlargement  of  the  end  of  the  filament  before  the 
formation  of  the  dome-shaped  columella,  which  cuts  off  the 
terminal  sporangium ;  (h)  a  sporangium  containing  develop- 
ing spores,  and  showing  the  position  of  the  columella. 

3.  The  end  of  a  stalk  (sporangiophore)  after  the  rupturing 
of  the  sporangium  wall,  exposing  the  columella. 

4.  A  group  of  spores  under  h.p. 


108  TYPE  STUDIES 

T>.  The  molds  have  a  method  of  sexual  reproduction,  but 
Rhizopus  nigricans  only  exhibits  it  if  certain  strains  hap- 
pen to  be  growing  together,  and  this  seems  to  occur  rarely 
in  nature  (see  Blakeslee,  Science,  Vol.  XIX,  p.  ^^A:,  1904  ; 
and  Proc.  Amer.  Acad.  Arts  and  Science,  Vol.  XL,  pp.  205- 
319, 1904).  Sporodinia  (Sec.  107),  however,  readily  develops 
zygospores.  Preparations  may  be  used  for  this  study 
(Sec.  212). 

Questions.  What  is  the  food  of  the  mold  ?  How  does  it 
obtain  its  food  ?  Can  solid  material  pass  through  the  wall 
of  the  filament  ?  How  does  it  happen  that  Rhizopus  springs 
up  so  readily  on  bread ?  Compare  the  structure  of  Rhizopus 
with  Vaucheria,  noting  points  of  similarity  and  difference. 

107.  Sporodinia.  This  form  grows  on  decaying  toadstools  and  mushrooms 
and  frequently  forms  zygospores  together  with  the  sporangia.  The  spores 
will  grow  readily  on  bread  and  other  media. 

A,  Study  zygospores  and  their  formation  from  living  or  preserved  mate- 
rial.   Draw  : 

1.  A  mature  zygospore  situated  between  two  filaments  called  suspen- 
sors.  Compare  their  walls.  Crush  the  zygospore  and  note  the  dense 
contents  full  of  oily  food  material. 

2.  Stages  in  the  formation  of  the  zygospore  showing  (a)  the  union  of 
the  tips  of  two  filaments,  (&)  the  cutting  off  of  teiTQinal  cells  or 
gametes  which  may  be  called  coenogametes  since  they  are  multinu- 
cleate, (c)  the  fusion  of  the  ccBnogametes  to  form  the  zygospores. 

B.  The  sporangia  of  Sporodinia  make  an  interesting  study  in  comparison 
with  those  of  Rhizopus. 

108.  Saprolegnia  or  Achlya,  water  molds.  Place  a  dead  fly,  or  a  pellet  of 
meat,  or  bits  of  bread  in  a  dish  containing  pond  or  ditch  water.  After  two 
or  three  days  note  the  gradual  development  of  a  halo  of  radiating  hyphse. 
Make  a  habit  sketch  of  the  growth  upon  the  substratum. 

A.  When  some  of  the  ends  of  the  hyphse  become  swollen  and  white  cut 
out  a  portion  of  the  mycelium  with  the  scissore  and  mount  in  water. 
Study  the  hyphae.  "What  is  their  structure  compared  with  that  of 
the  molds  ?  Draw  a  tip  showing  arrangement  and  character  of  the 
protoplasm. 

B.  Examine  the  swollen  tips,  some  of  which  should  be  sporangia  with 
zoospores  in  various  stages  of  development.    Draw  under  h.p. : 

1.  A  mature  sporangium  full  of  zoospores. 

2.  Stages  in  the  development  of  sporangia. 


ALBUGO  *  109 

3.  Watch  for  the  escape  of  zoospores,  which  ahiiost  always  takes  place 
from  mature  sporangia,  when  mounted  on  the  slide,  probably  because 
of  the  somewhat  changed  conditions  of  temperature  and  density  of  the 
water.  Observe  whether  the  zoospores  swim  away  at  once  (generally 
Saprolegnia)  or  immediately  come  to  rest  near  the  opening  of  the 
sporangium  (generally  Achlya). 

4.  Stain  the  zo(3spores  with  iodine  to  show  cilia. 

C.  Watch  for  the  development  of  oogonia  as  clusters  of  minute  spher- 
ical structures,  generally  situated  nearer  the  substratum  than  the 
sporangia.     Observe  : 

1.  That  the  oogonium  develops  a  number  of  eggs.    Count  them.  Draw. 

2.  Whether  delicate  anther idial  filaments  are  present,  growing  over  the 
surface  of  the  oogonia  and  entering  them.  Draw,  if  present,  and 
study  their  origin. 

109.  Albugo,  the  blister  blight.  This  parasite  is  common  on  the  shepherd's 
purse  (Capsella),  wiiich  is  the  most  convenient  host  for  laboratoiy  study. 
Note  the  appearance  of  white  blisters,  the  conidial  fructification,  on  leaves 
and  stems.  The  sexual  fructification,  more  common  on  the  radish,  occurs 
in  the  interior  of  stems  and  leaves,  which  become  swollen  and  purplish  in 
color.    Make  a  habit  sketch  of  the  blisters. 

A.  Study  sections  of  the  blisters  cut  free-hand  in  pith  or  preparations  cut 
on  the  microtome  (Sec.  212).    Draw  : 

1.  An  outline  of  the  section  showing  (a)  the  position  of  the  epidermis, 
(6)  the  chains  of  air  spores,  or  conidia^  wdiich  raise  the  epidermis 
from  the  tissue  beneath,  and  (c)  the  position  of  the  conidiophores, 
structures  from  which  the  conidia  develop. 

2.  Under  h.p.  the  details  of  a  group  of  conidiophores,  showing  the 
manner  in  which  the  conidia  develop  and  the  relation  of  the  conidio- 
phores to  the  mycelium  in  the  interior  of  the  host. 

3.  Study  the  mycelium  between  the  cells  of  the  host.  Search  for 
sucker-like  processes,  haustoria,  penetrating  the  host  cells.  A  portion 
of  infected  tissue  boiled  for  a  few  minutes  in  a  dilute  potash  solution 
(five  per  cent)  and  then  teased  out  will  give  excellent  preparations. 

B.  Study  sections  of  tissue  with  the  sexual  organs.    Note  and  draw  : 

1.  The  large  oogonia,  the  oldest  ones  containing  each  a  single  oospore 
with  a  heavy  cell  wall. 

2.  Younger  oogonia  in  which  the  egs;  is  present  as  a  region  of  denser 
ooplasm,  separated  from  a  surrounding  periplasm ;  also  younger 
stages  before  the  egg  is  differentiated  in  the  oogonium. 

3.  Favorable  sections,  if  present,  showing  the  club-shaped  antkeridiuin 
at  the  side  of  the  oogonium  and  the  beak-like  process  which  it  puts 
forth,  penetrating  the  ortgoniuniand  growing  through  the  periplasm 
to  the  egg. 


110  ■  TYPE   STUDIES 

THE  SAC  FUNGI,  OR  ASCOMYCETES 

110.  Field  work  on  the  sac  fungi  and  basidia  fungi.  The  groups  of  higher 
fungi,  Asconiycctes  and  Basidioniycetes^  raay  readily  be  studied  together  in 
the  field,  since  representatives  of  both  are  usually  found  in  the  same  situa- 
tions.   There  are  several  sorts  of  localities  which  furnish  abundant  supplies. 

(1)  Wet,  shaded  woods  and  the  borders  of  shaded  swamps  will  give  the 
larger  forms  of  cup  fungi  and  their  relatives,  and  certain  basidia  fungi. 

(2)  Open  woods,  especially  along  woodland  paths,  are  excellent  situations 
for  the  fleshy  gill,  pore,  and  tooth  fungi,  while  stumps,  logs,  and  fallen 
branches  furnish  material  of  the  woody  basidia  fungi  and  the  knot  and  wart 
fimgi.  (3)  Pastures  and  the  edges  of  woodland  are  favorable  situations  for 
certain  gill  fungi  and  puffballs,  (4)  Lichens  grow  under  a  great  variety  of 
conditions,  from  those  of  bare  soil  and  rocks  to  much  shaded  situations  on 
tree  trunks.  (5)  The  parasitic  forms  have  for  the  most  part  their  own 
peculiar  life  habits  associated  with  various  hosts.  Collections  of  conspicuous 
forms  should  be  made  with  careful  notes  on  the  life  conditions,  and  the  forms 
brought  to  the  laboratory  for  identification,  at  least  so  far  as  the  chief  groups 
are  concerned.  The  woody  and  firm  fungi  (including  lichens)  and  many 
parasitic  forms  on  leaves  may  be  dried  or  pressed  as  one  would  any  plant. 
Fleshy  fungi  must  be  preserved  in  strong  alcohol. 

111.  Microsphaera,  the  lilac  mildew.  Study  its  habit  of  growth 
on  the  lilac.  Where  is  it  most  luxuriant  ?  Describe  the  appear- 
ance of  the  mycelium  on  the  leaves.  Try  to  find  leaves  that 
appear  powdery  because  of  the  conidial  fructification,  commonest 
in  the  summer  time.  Note  the  position  of  the  ascocarps  or  sac 
fruits,  appearing  as  black  dots. 

A.  The  ascocarps.  Sketch  the  outline  of  a  leaf  and  show  the 
distribution  of  the  mycelium  with  its  ascocarps.  Moisten  the 
surface  with  a  dilute  potash  solution,  and  with  a  scalpel 
scrape  off  some  of  the  mycelium  and  sac  fruits. 

1.  Note  the  character  of  the  hyphm,  their  branching,  the 
occasional  cross  partitions,  and  the  cell  contents. 

2.  Draw  an  ascocarp  with  one  or  more  of  its  appenthKjes  in 
detail.  What  is  the  structure  of  the  wall  of  the  fruit  and 
the  tips  of  tlie  a])pendages  ?  Note  the  number,  form,  and 
distribution  of  the  latter. 


MICROSJ'ILERA  111 

3.  Crush  the  ascocarps  carefully  by  pressure  on  the  cover 
glass  with  the  tip  of  a  scalpel  while  watching  them  under 
the  microscope.  Observe  the  escape  of  the  sacs,  called 
ascl,  containing  spores.    Note  their  number  and  form. 

4.  Draw  an  ascus,  or  group  of  asci  with  the  spores,  ascospores. 
What  is  the  number  of  spores,  their  form  and  arrange- 
ment ?  Show  these  points  in  your  drawings.  The  sexual 
organs  of  the  mildews  are  small  and  not  easily  studied 
(see  Frinciples,  Fig.  219,  and  the  paper  by  Harper,  "  Sex- 
ual Keproduction  and  the  Organization  of  the  Nucleus  in 
Certain  Mildews,"  Carnegie  Institution  of  Washington, 
Publication  No.  37,  1905). 

B.  The  conidial  fruit.  Moisten  with  a  potash  solution  the 
surface  of  a  leaf  which  appears  powdery  and  scrape  off  the 
mycelium.  Observe  the  upright  filaments,  or  conidiophores, 
which  develop  terminally  a  chain  of  air  spores,  or  conidia. 
Other  types  of  the  mildews  are  frequently  better  for  the 
study  of  the  conidial  fructification,  as,  for  example,  ^tysipke. 

Questions.  Is  there  mycelium  of  the  mildew  in  the  interior 
of  the  host  ?  How  does  it  obtain  its  nourishment  ?  Which 
forms  of  spores,  conidia  or  ascospores,  might  serve  better 
to  carry  the  fungus  over  unfavorable  seasons,  and  which  to 
multiply  the  plants  during  the  growing  season?  Describe 
the  life  history  of  the  lilac  mildew. 

112.  Penicillium  and  Aspergillus,  the  green  and  yellow  mildews.  The  green 
mildew,  or  "  mold,"  Penicillium.,  is  a  very  common  form  and  begins  to  appear 
on  bread  shortly  after  the  i)read  mold  has  reached  a  luxuriant  development. 
On  what  other  substances  have  you  observed  the  green  mildew  growing  ? 
The  yellow  mildew,  Aspergillus.,  may  be  obtained  on  cheese  in  a  moist 
chamber  and  is  not  uncommon  on  damp  leather,  herbarium  material,  and 
other  substances  that  "  mildew.'"  The  fructifications  of  these  two  forms  are 
generally  conidial.    Describe  their  appearance, 

A.  Conidial  fructifications.  Place  a  small  quantity  of  the  fructitication 
on  a  slide  in  a  drop  of  alcohol  (to  drive  out  air  bubbles),  followed  by 
water.  Distribute  the  material  well  and  mount.  iStudy  under  the 
highest  magnification  : 


112  TYPE  STUDIES 

1.  The  spore-bearing  stalks  (conidiophores),  with  a  portion  of  the 
mycelium.  Note  the  cross  walls  and  the  arrangement  of  the  conidia 
and  their  formation.    Draw  in  detail. 

2.  Diagram  and  compare  the  fructifications  of  Penicillium  and  of 
Aspergillus. 

B.  Some  species  of  Asj)ergillus  not  infrequently  develop  ascocarps  (for- 
merly included  in  the  genus  Eurotium).  Study  their  structure  in  com- 
parison with  the  sac  fruit  of  the  lilac  mildew. 

113.  Peziza,  Lachnea,  or  other  cup  fungi. 

A.  Study  the  general  form  of  the  cups,  which  are  sac  fruits  or  ascocarps, 
and  their  relation  to  the  substratum.  Where  is  the  vegetative  mycelium 
of  the  fungus  ?  Tap  the  cup  of  large  forms,  if  living,  and  note  the  dis- 
charge of  a  smoky  cloud  of  spores.    Make  habit  sketches. 

B.  Section  the  cup  in  pith  with  a  razor,  or  study  sections  cut  with  the 
microtome  (Sec.  212).  Draw  first  an  outline  sketch  showing  the  rela- 
tion of  the  parts,  and  then  details.     Note  : 

1.  The  fruiting  surface  containing  the  spore  sacs,  asci,  in  various  stages 
of  development  among  sterile  filaments,  paraphyses. 

2.  The  relation  of  the  fruiting  surface  to  the  dense  web  of  interwoven 
hyphse  beneath. 

3.  Study  stages  in  the  development  of  the  asci  and  ascospores. 

C.  Some  of  the  larger  fleshy  Ascomycetes  related  to  the  cup  fungi  are 
excellent  for  comparative  studies,  or  substitutes.  Such  are  the  morel 
(Morchella),  Helvella,  Geoglossuin,  Mitrula^  etc. 

114.  Knot  and  wart  fungi.  Material  of  the  black  knot  {Plowrightia)  and 
the  larger  wart  fungi,  such  as  Daldinia,  Ilypoxylon,  Xylaria,  etc.,  furnish 
excellent  studies  in  comparison  with  the  cup  fungi. 

A.  Study  the  growth  habits  of  the  forms. 

B.  Section  with  an  old  razor  the  sac  fruits,  ascocarps,  noting  that  the  sacs 
are  contained  in  special  cavities,  perithecia,  opening  to  the  exterior. 

115.  Other  sac  fungi.  Many  other  sac  fungi  are  interesting  types  for 
study  if  material  and  time  are  available.  Among  them  are  ergot  {Clavi- 
ceps),  caterpillar  fungi  (Cordyceps),  truffles,  some  of  the  spot  fungi  and  rots. 
Certain  of  these  sac  fungi  have  remarkable  forms  of  conidial  fructifications 
well  worth  study,  as  have  also  many  of  the  imperfect  fungi. 

116.  Physcia,  Parmelia,  or  other  lichen**  (App.  16). 

A.  Study  the  form  of  the  lichen,  whether  closely  pressed 
against  the  substratum  (crustaceous),  lobed  and  leaf-like 
(foliose),  or  much  branched  (fruticose).  Describe  its  sub- 
stratum; attachment,  color,  and  form.     Search  for  fruiting 


THE  LICHEN  113 

regions,  frequently  in  the  form  of  cups,  called   apothecia. 
Draw  habit  sketches. 

B.  Section  in  pith  with  a  razor  a  medium-sized-  fruit  (first 
moistened).  Draw  first  an  outline  sketch,  showing  the  rela- 
tion of  parts,  and  then  details.    Note  : 

1.  That  there  are  two  elements  in  the  lichen  :  {(f)  green  or 
blue-green  cells  ;  (b)  colorless  regions  made  up  of  filaments 
more  or  less  densely  interwoven. 

2.  Study  in  detail  the  green  or  blue-green  cells  under  h.p., 
comparing  their  structure  with  the  algal  types  that  have 
been  studied. 

3.  Examine  the  colorless  regions,  comparing  their  structure 
with  such  types  of  fungi  as  have  been  studied. 

4.  Study  in  detail  the  fruiting  surface.  Is  it  algal  or  fun- 
gal in  character,  and  to  what  types  is  it  clearly  related  ? 
Draw  carefully  its  structure. 

C.  Study  from  sections  the  strictly  vegetative  parts  of  the 
lichen  with  reference  to  the  distribution  of  the  parts  com- 
posing it,  and  especially  the  structure  of  the  lower  surface 
where  it  comes  in  contact  with  the  substratum. 

D.  Search  for  scales,  called  soredia,  on  the  surface  of  some 
lichens.  These  scales  contain  algal  cells  inclosed  in  a  net- 
work of  hyphie,  and  falling  off  the  parent  plant  may  develop 
new  lichens,  thus  constituting  a  very  effective  means  of 
vegetative  propagation. 

TvKFERENCE.    Principles,  Sec.  271 ;    Schneider,  42. 

Questions.  AVliat  are  your  conclusions  on  the  structure  and 
composition  of  a  lichen  ?  What  are  its  methods  of  repro- 
duction ?  How  do  new  lichens  develop  ?  Describe  tlie  life 
habits  of  lichens  and  their  effect  on  such  substrata  as  rocks, 
trees.  Under  what  conditions  do  they  grow  most  vigor- 
ously. How  do  they  survive  periods  of  drought  and  cold  ? 
What  is  the  food  of  a  lichen  and  how  is  it  obtained  V  How 
do  the  algae  benefit  the  fungus  in  the  lichen'-?  Does  the 
alga  receive  equivalent  benefit  from  the  fungus  ? 


114  TYPE   STUDIES 

THE  BASIDIA  EUNGI,  OK  BASIDIOMYCETES 

117.  The  smuts.  The  corn  smut,  Ustilac/o  Maijdis,  is  excellent  for  demon- 
stration, but  some  of  the  smaller  forms  found  on  oats,  wheat,  many  grasses, 
and  Juncus  are  frequently  more  convenient  for  laboratory  work. 

A.  Study  the  fructification  on  the  host.  Observe  the  parts  infected  and 
the  extent  of  the  injury.    Make  habit  sketches. 

B.  Tease  out  part  of  the  fructification  in  water.  Draw  the  resting  cells 
known  as  chlamydospores  or  teleutospores.  Does  their  structure  indicate 
that  they  are  resting  spores  capable  of  carrying  the  fungus  over  un- 
favorable seasons  of  drought  or  cold  ?  Why  ?  Sections  of  the  infected 
tissue  just  before  the  formation  of  the  chlamydospores  are  necessary 
to  an  understanding  of  their  development. 

C.  Place  some  of  the  chlamydospores  in  a  dilute  decoction  of  manure, 
previously  sterilized  by  boiling,  or  make  a  culture  in  a  hanging  drop 
(Sec.  204).  The  spores  germinate  better  after  being  frozen.  Observe 
the  cultures  from  day  to  day  and  trace  the  germination  of  the  spores 
and  the  development  from  each  of  a  short  filament,  pro77iycelium, 
which  gives  rise  to  thin-walled,  delicate  sporidia,  or  spring  spores. 

118.  Puccinia  graminis,  the  wheat  rust.  It  is  somewhat  easier 
to  begin  the  study  with  the  stage  knov/n  as  black  rust. 

A.  The  black  rust.  Study  the  distribution  of  the  black  rust  on 
the  stems  and  leaves  of  wheat  or  various  grasses.  Make 
habit  sketches.  At  what  time  does  the  black  rust  appear 
on  the  wheat? 

1.  Scrape  out  the  contents  of  a  spot  and  examine  in  water 
under  h.p.  Note  the  color  of  the  resting  cells,  which  are 
really  chlamydospores,  although  generally  called  teleuto- 
spores, or  winter  spores.  These  spores  are  always  two- 
celled.    Draw  in  detail. 

2.  Section  the  leaves  or  stem  in  pith  (soaking  dried  material  first  in 
potash  solution),  or  study  sections  cut  with  a  microtome  (Sec.  212). 
Note  the  clusters  of  teleutospores,  each  on  a  stalk,  and  the  relation 
of  the  latter  to  the  mycelium  within  the  liost.  Examine  the  distor- 
tion (hypertrophy)  of  the  host  tissue  in  the  infected  region.  Show 
tliese  points  in  a  large  figure  or  series  of  figures. 

B.  The  red  rust.  Study  the  distribution  of  the  spots  of  red 
rust.    Habit  sketch.    At  what  time  does  the  red  rust  appear 


PUCCINIA  ,  115 

on  the  wheat  ?    When  is  it   present  in  greatest  quantity  ? 
What  effect  does  it  have  on  the  host  ? 

1.  Scrape  out  the  contents  of  a  spot  and  examine  under 
h.p.  Note  the  color  and  form  of  the  spores,  called  vredo- 
spores,  or  summer  spores.  These  spores  are  always  one- 
celled.    Draw. 

2.  Study  sections  of  the  leaves  (Sec.  212),  as  for  the  telentospores,  and 
note  the  origin  of  the  uredospores  and  their  relation  to  the  mycelium 
of  the  host.    Show  these  points  in  a  large  figure. 

C.  The  cluster  cifps  on  barberry.  Examine  the  infected  barberry 
leaves,  making  a  habit  sketch  of  the  lower  side.  Draw  the 
spots  under  a  hand  lens,  noting  (1)  on  the  lower  side  rela- 
tively large  cluster  cups,  or  wcidia,  containing  cvcidiospores ; 
(2)  on  the  upper  side  minute  crater-like  openings  marking 
the  sjyermogonia. 

1.  Scrape  out  the  contents  of  a  cluster  cup  and  draw  the 
secidiospores  under  h.p. 

2.  Section  the  spots  in  pith  or  study  sections  cut  with  a  microtome 
(Sec.  212).  Note  (a)  the  formation  of  the  secidiospores  in  chains 
from  a  fruiting  surface  ;  (b)  that  the  wall  of  the  cluster  cup,  perid- 
ium^  is  a  cell  membrane  composed  of  rows  of  modified  spores 
adhering  together  ;  (c)  the  small  spermogonia  filled  with  very  deli- 
cate converging  filaments  which  develop  terminally  bacterioid  bod- 
ies, believed  to  be  degenerate  sperms  and  called  spermatia ;  [d)  the 
general  relation  of  these  parts  to  the  tissue  of  the  host.  Show  these 
points  in  a  large  figure  or  series  of  figures. 

Keference.    PrincipleSj  Sec.  275. 

Questions.  Why  are  the  telentospores  thick  w^alled  ?  What 
do  they  develop  on  germination  (see  Principles,  Fig.  231)? 
Outline  carefully  the  life  history  of  the  wheat  rust  from 
your  laboratory  study  and  reading.  Compare  this  life  history 
with  that  of  the  smut,  noting  the  phases  that  correspond 
with  one  another.  Does  the  barberry  grow  in  your  section 
of  the  country,  and  if  so  does  it  produce  cluster  cups?  If  it 
does  not  grow  there  how  may  the  life  history  of  the  rust 
be  modified? 


116  TYPE  STUDIES 

119.  Pore  and  tooth  fungi.  Study  representatives  of  the  pore  or  tooth  fungi 
in  the  field.    Note  whether  they  are  parasites  or  saprophytes. 

A.  Observe  their  form,  attachment,  and  relation  to  the  substratum. 
Examine  some  of  the  bracket  types  with  reference  to  their  position 
in  relation  to  the  surface  of  the  earth.  What  must  be  the  determin- 
ing influence  in  shaping  their  manner  of  growth  ?  Make  habit  sketches. 
These  structures  are  fructifications.  Where  is  the  vegetative  mycelium  ? 

B.  Note  the  fruiting  surface,  or  hymenium,  lining  cylindrical  pores  in  the 
pore  fungi  (Fam.  PolyporacecR)  and  distributed  over  teeth  in  the  tooth 
fungi  (Fam.  Hydnaceoi).  Cut  into  the  fructifications  to  ascertain  the 
structure  and  position  of  the  pores  or  teeth.    Draw  in  detail. 

120.  Agaricus,  Coprinus,  Amanita,  or  other  gill  fungus  *  *  (App. 
17).  Study  the  type  when  possible  in  the  field.  Is  it  a  sapro- 
phyte or  2,  jjarasite?  The  toadstool  is  a  fructification.  Where  is 
the  vegetative  mycelium  ?  Dig  up  the  earth  around  the  base  of 
the  toadstool  and  wash  carefully.  Examine  the  white  strands  of 
the  mycelium  under  the  microscope.    A  re  they  single  hyph^e  ? 

A.  The  fructification.  Note  the  three  parts  always  present  in 
a  toadstool :   (1)  ih-Q  stalk,  or  stipe;   (2)  the  cap,  ov  pileus  ; 

(3)  the  gills,  or  lamellce,  on  the  under  side  of  the  cap.  In 
addition  to  these  parts  there  are  present  in  certain  genera 

(4)  either  a  cup  or  volva,  or  both,  from  the  interior  of 
which  the  stalk  rises,  and  (5)  a  ring  around  the  stalk  just 
beneath  the  cap.  The  ring  is  the  remains  of  a  veil,  present 
at  a  certain  stage  of  development,  connecting  the  margin  of 
the  cap  with  the  stalk.  Portions  of  the  volva  are  found  in 
some  forms  as  scales  on  the  top  of  the  cap.  Show  these 
structures  in  a  habit  sketch. 

1.  Examine  in  some  detail  the  position  of  the  gills  on  the 
cap,  their  color  and  texture,  and  also  that  of  the  stalk. 
Divide  the  toadstool  lengthwise  to  determine  these  points. 

2.  Section  the  gills  in  pith  or  study  sections  cut  with  a  microtome 
(Sec.  212).  Note  the  structure  of  the  fruiting  surface,  or  hymenium, 
containing  hasidia.,  each  of  which  develops  four  spores,  hasidiospores, 
on  short  stalks,  sterigmata.  The  common  mushroom  of  the  market, 
Agaricus  campestris,  develops  only  two  spores  on  each  basidium. 
Observe  the  relation  of  the  basidia  to  a  network  of  hyphie  in  the 


A(JARTC[JS  117 

interior  of  tlie  gill  and  note  their  position  among  the  sterile  rells  in 
the  hymenium.    Show  these  points  in  a  detailed  drawing. 
3.   Observe  the  color  of  the  spores,  best  determined  by  spore  prints; 
obtained  when  the  pileus  is  cut  off  the  stalk  and  placed  gill  side 
down  on  a  sheet  of  paper  and  left  over  night  under  a  bell  jar  or 
tumbler.    Use  black  paper  if  the  gills  are  white. 
B.  Development  of  the  fructification.    Study  the  young  ''  but- 
ton"  stages    of   the  toadstool.    Cut  them   lengthwise  and 
determine  the  position  of  the  parts  of  the  mature  fructifica- 
tion.   This  examination  should  make  clear  the  relation  of 
the  stalk  to  the  cap  above  and  the  cup  below,  if  present. 
Note  that  the  gills  are  developed  in  a  chamber  whose  roof 
is  the  cap  and  whose  floor  is  the  veil,  finally  ruptured  by 
the  expansion  of   the   cap   and  remaining   as  the  ring  in 
some  types.    Illustrate  these  points  in  outline  sketches  or 
diagrams. 
Qup:stions.    What  seasonal  conditions  are  best  for  gill  fungi, 
and  what  for  fleshy,  pore,  and  tooth  fungi  ?    Describe  the 
habits  of  growth  of  gill  fungi  in  pastures  and  lawns.    What 
is  a  fairy  ring  ?    Can  you  account  for  its  form  ?    Do  you 
know  of  any  parasitic  gill  fungi  attacking  trees  ? 

121.  Puffballs,  earth  stars,  and  nest  fungi.  Study  types  in  the  field  in 
reference  to  the  substratum.  Where  are  the  vegetative  portions  of  the  plant  ? 
Examine  the  fructifications  in  various  stages  of  development.  Make  habit 
sketches. 

1.  Cut  sections  lengthwise  and  observe  the  texture  of  the  envelopes  inclos- 
ing the  spore  chamber.  Note  the  way  in  which  the  chamber  opens  and 
the  spores  are  distributed. 

2.  In  the  spore  chamber  observe  the  fibrous  remains  of  sterile  tissue  and 
the  powdeiy  spores.  The  nest  fungi  exhibit  special  complexities  in  the 
form  of  egg-like  structures  which  contain  the  spores. 

THE  LIVERWORTS,  OR  HEPATIC^ 

122.  Field  work  on  the  liverworts  and  mosses.  The  liverworts  and  mosses 
can  be  advantageously  studied  together  in  the  field  since  many  species  of 
both  groups  grow  in  similar  situations.  The  chief  types  of  localities  are 
(1)  wet  swamps,  especially  Sphagnum  bogs,  frequented  by  other  mosses  and 


118  TYPE   STUDIES 

certain  thalloid  liverworts  ;  (2)  wet  margins  of  ponds  and  swamps  and  wet 
meadows,  sometimes  supplying  Marchantia  abundantly  and  many  mosses ; 
(3)  the  surface  of  small  ponds  and  the  mud  around  their  borders  occasionally 
abounding  in  Riccia  and  Ricciocarpus  ;  (4)  wet  rocks  along  shaded  streams, 
walls  of  gorges  and  entrances  to  caverns  frequently  with  veiy  extensive 
growths  of  liverworts,  Marchantia,  Conocephalus,  Pellia,  etc.;  (5)  base  and 
sides  of  trees  in  damp,  shaded  woods,  rocks  and  the  ground  in  similar  situa- 
tions covered  with  mats  of  leafy  liverworts  and  mosses,  often  mixed  together 
in  confusion,  but  some  types  presenting  characteristic  habits  of  growth  ; 
(6)  dry  earth  in  more  open  woods,  pastures,  bare  hillsides,  etc. ,  with  a  number 
of  characteristic  types  of  mosses  but  no  liverworts.  Notes  should  be  taken 
on  the  life  habits,  especially  with  reference  to  the  texture  of  the  forms  in 
relation  to  the  conditions  of  moisture.  Collections  may  be  made  and  brought 
to  the  laboratory  for  study.  For  city  classes,  abundant  growths  of  Lunularia 
and  Marchantia  may  frequently  be  found  in  greenhouses,  especially  those 
not  well  kept,  together  with  many  mosses  and  their  protonemata. 

123.  Ricciocarpus.   Most  species  of  Riccia  may  also  be  studied  by  this 
outline.    If  living  material  is  available,  observe  carefully  the  life  habits. 

A.  General  morphology.    Note  : 

1.  The  upper  and  lower  surfaces  of  the  thallus.  How  are  they  distin- 
guished ? 

2.  The  form  of  the  plant,  method  of  branching. 

3.  The  notched  tips  or  forward  ends  of  the  branches  where  are  situated 
the  growing  points.    How  do  the  plants  reproduce  vegetatively  ? 

4.  A  shallow  furrow,  thickened  somewhat  on  the  lower  side  like  a 
midrib,  running  into  each  lobe,  forking  when  the  thallus  forks,  and 
ending  in  the  growing  points. 

6.  The  position  of  globular  bodies,  the  older  ones  black,  imbedded  in 
the  denser  tissue  along  the  furrow.  These  are  sporophytes,  frequently 
called  the  fruit  of  the  liverwort.  What  is  the  relative  arrangement 
of  the  younger  and  older  sporophytes  ? 

6.  Examine  the  structure  and  distribution  of  membranous /rmgfes  and 
delicate  filaments,  rhizoids,  on  the  lower  surface.  Cut  off  some  of 
these  and  examine  under  m.p.    What  are  their  functions?   Draw. 

Draw  a  habit  sketch  of  the  upper  surface,  showing  points  discussed 
above. 

B.  Structure  of  the  thallus.    Cut  sections  in  pith  across  the  thallus  and 
through  the  sporophytes  when  possible.    Note  : 

1.  The  cell  structure  of  the  upper  and  lower  surfaces  as  compared  with 
one  another.    Where  are  the  chloroplasts  chiefly  found  ? 

2.  The  position  and  attachment  of  the  fringes  and  rhizoids. 

C.  Structure  of  the  sporophyte.   Study  sections  of  the  sporopyhtes  with 
developing  or  mature  spores.    Note  : 


MARCHANTIA  119 

1.  That  the  sporopliyte  is  contained  witliin  a  celhilar  envelope,  calyptra. 
Observe  the  positions  of  IJie  sporophytes  witli  relation  to  the  midrib 
region  of  the  thallus. 

2.  That  tlie  sporophyte  has  a  delicate  wall  composed  of  a  layer  of  cells 
within  the  calyptra,  and  contains  developing  or  mature  spores. 

3.  That  the  spores  are  formed  in  groups  of  four,  tetrads,  within  spore 
mother  cells. 

4.  The  markings  on  the  walls  of  mature  spores. 

5.  In  median  sections  the  shriveled  remains  of  the  neck  of  the  arcJie- 
gonlum,  whose  very  much  enlarged  base  is  now  the  calyptra. 

Illustrate  as  many  of  these  points  as  possible  in  a  semidiagrammatic 
drawing. 
D.    The  structure  of  the  sexual  organs  and  development  of  the  sporophyte. 

These  are  best  studied  from  lengthwise  sections  cut  in  paraffin  with 

the  microtome  and  stained. 
Reference.    Campbell,  23. 

124.  Marchantia.  It  is  well  to  examine  first,  in  comparison 
with  one  another,  male  and  female  plants  and  those  devoted 
chiefly  or  exclusively  to  bud  formation.  In  living  material  study 
the  growth  habits  in  relation  to  earth,  dampness,  and  light. 

A.    General  morphology.    Note  : 

1.  The  upper  and  lower  surfaces.  How  are  they  distin- 
guished ? 

2.  The  ribbon-like  form  of  the  thallus,  the  method  of  branch- 
ing. Is  it  a  mode  of  forking,  and  why  are  the  branches 
irregular  in  length  ? 

3.  The  notched  tips  of  the  branches  where  the  cji^oicing points 
are  situated.  Find  a  specimen  whose  tip  has  recently 
branched  so  that  there  are  two  growing  points  close 
together  but  diverging. 

4.  A  central  line,  or  midrib,  running  into  each  branch,  forking 
when  the  thallus  forks,  and  ending  in  the  growing  points. 

5.  The  character  of  membranous /rmp'es  and  filaments,  rJti- 
zoids,  on  the  lower  surface,  and  their  distribution  with 
especial  reference  to  the  midrib  region. 

6.  The  presence  of  stalked  disks  or  nmbrella-Uke  structures, 
which  bear  the  sexual  organs,  or  of  cups,  containing  Imds. 

Illustrate  as  many  of  these  points  as  possible  in  sketches. 


1'20  TYPK   STUJ^IKS 

B.  Structure  of  the  thai] us. 

1.  Examine  the  upper  surface  with  a  hand  lens.  Draw  a 
portion  showing  the  diamond-shaped  areas,  each  with  a 
central  pore. 

2.  Cut  cross  sections  in  pith  and  compare  the  cell  structure 
of  the  upper  and  lower  surfaces.  iSTote  the  air  chambers, 
opening  to  the  outer  air  through  the  pores,  and  containing 
hTsmching  filaments  of  ovoid  cells  with  large  and  numer- 

'  ous  chloroplasts.    From  your  knowledge  of  leaf  structure, 

what  would  seem  to  be  the  functions  of  the  air  chambers 
and  green  filaments  ?  Study  the  structure  of  the  thallus 
below  the  air  chambers. 

3.  Examine  the  attachment  and  structure  of  the  fringes  and 
rhizoids. 

Draw  a  cross  section  illustrating  the  above  points.  Micro- 
tome sections  of  the  thallus  (Sec.  212)  will  show  cer- 
tain details  more  clearly,  as,  for  example,  the  structure 
of  the  pores,  but  they  should  be  used  only  in  compari- 
son with  sections  of  the  living  plant,  in  which  the  dis- 
tribution of  the  chlorophyll-bearing  tissue  may  best  be 
studied. 

C.  TJte  cups  or  cupides} 

1.  Draw  a  euj)  somewhat  magnified  as  it  appears  on  the  sur- 
face of  the  thallus,  showing  the  buds,  or  gemime,  within. 
Are  cups  found  on  the  same  thallus  with  the  stalked  disks 
and  umbrella-like  structures  ? 

2.  Examine  a  bud  under  m.p.,  noting  the  two  notches  on 
opposite  sides,  which  are  growing  points,  and  the  scar 
where  it  was  attached  to  a  stalk. 

3.  Search  for  young  Marchantia  plants  developing  from 
buds. 

4.  Section  a  cup  in  pith,  and  study  the  development  of  the  buds  and 
their  attachment. 

1  Lunularia,  a  relative  of  Marchantia  and  frequently  common  in  greenhouses, 
has  a  cup  of  quite  different  form,  but  otherwise  agrees  closely  with  Marchantia 
and  may  be  substituted  for  it. 


.MAKCIIANTTA  121 

D.  TJie  antheridia,  or  male  se,ruaJ  organs.  These  are  Iwriie  on 
stalked  disks,  with  scalloped  margins,  and  are  called  anther- 
idial  receptacles,  or  antherldiophores. 

1.  Draw  an  antheridial  receptacle,  showing  its  relation  to 
the  thallus  and  the  number  and  form  of  the  lobes  of  the 
disk.  Where  is  it  situated  with  reference  to  the  midrib 
of  the  thallus  ? 

2.  Section  the  disk  in  pith.  Note  the  antheridla  situated 
in  cavities  among  the  irregularly  shaped  air  chambers. 
Where  are  the  youngest  antheridia  found  ?  Make  a  semi- 
diagrammatic  sketch  showing  these  points. 

3.  Study  the  structure  of  an  antheridium.  Observe  the 
short  stalk  and  the  cellular  sperm,  case  above.  If  the 
antheridia  are  not  sectioned,  crush  and  note  the  contents 
of  older  structures  which  will  probably  show  the  minute 
developing  sperms.  Staining  the  material  with  iodine 
may  bring  out  some  points  more  clearly. 

4.  Microtome  sections  of  the  antheridial  receptacles  (Sec.  212)  will  give 
abundant  stages  in  the  development  of  the  antheridia  and  sperms, 
and  show  clearly  the  structure  and  arrangement  of  the  sperm  mother 
cells  within  the  mature  antheridium. 

E.  The  archegonia,  or  female  sexual  organs.  These  are  borne  on 
stalked  structures,  with  long,  finger-like  processes  arranged 
like  the  ribs  of  an  umbrella,  and  are  called  archegonial  recep- 
tacles, or  archegoniophores.  Are  antheridial  and  archego- 
nial receptacles  ever  found  on  the  same  plant  ?  Are  cups 
found  on  these  plants  ? 

1.  Draw  an  archegonial  receptacle,  showing  its  relation  to 
the  thallus  and  the  number  and  arrangement  of  its  finger- 
like processes.  Where  is  it  situated  with  reference  to  the 
midrib  of  the  thallus  ? 

2.  Draw  a  view  of  the  receptacle  as  seen  from  below,  choos- 
ing an  old  specimen.  Older  material  will  present  sporo- 
phytes,  frequently  called  the  fruits  of  the  liverwort,  in 


122  •  TYPE   STUDIES 

various  stages  of  development.  Observe  their  arrange- 
ment in  lines  between  fringes.  Where  are  the  oldest 
sporophytes  situated  ? 

3.  Make  sections  in  pith  across  rather  young  or  medium- 
sized  receptacles.  Some  of  them  will  show  the  flask- 
shaped  archegonia  of  various  ages.  Note  the  swollen  base, 
or  venter,  and  the  neck.  If  the  archegonium  be  not  fully 
mature,  a  line  of  canal  cells  is  to  be  seen  in  the  neck,  ter- 
minating in  the  large  egg  within  the  swollen  base.  Illus- 
trate these  points  in  figures. 

4.  Hunt  for  older  stages  following  the  opening  of  the  neck 
and  fertilization  of  the  Qg%.  Note  the  shriveled  neck  and 
much  enlarged  base,  which  now  contains  a  developing 
sporophyte.  The  older  fertilized  archegonia  become  sur- 
roimded  by  an  open,  sac-like  envelope  (perianth)  which 
develops  at  their  base. 

5.  Make  sections  of  the  stalk  and  examine  under  m.p.,  noting  the  two 
grooves  containing  rhizoids.  Follow  these  grooves  up  and  down  on 
the  stalk,  and  trace  them  to  the  point  where  the  stalk  joins  the 
thallus.  What  is  the  significance  of  the  rhizoids  in  the  grooves? 
What  relation  does  the  stalk  bear  to  the  thallus  ? 

6.  Microtome  sections  of  the  archegonial  receptacles  (Sec.  212)  are  al- 
most essential  to  an  understanding  of  the  development  and  arrange- 
ment of  the  archegonia  and  their  minute  structure.  They  also  show 
stages  in  the  development  of  the  sporophyte. 

F.  The  sporophyte.  Section  old  archegonial  receptacles.  Also 
pick  off  some  of  the  sporophytes  which  have  opened  and  are 
discharging  spores,  and  mount  them  entire.  Note  and  show 
in  drawings : 

1.  That  the  mature  sporophyte  consists  of  ^  spore  case  borne 
on  a  stalk  attached  by  a/oof  to  the  base  of  the  archegonium. 
The  latter  has  been  ruptured  by  the  development  of  the 
sporophyte. 

2.  That  the  spore  case  at  maturity  opens  and  discharges  the 
spores  which  lie  among  a  tangle  of  spirally  marked  fila- 
ments called  elaters. 


PORELLA  123 

3.  INIicrotonie  sections  of  (he  sporopliytes  (Sec.  212)  arc  necessary  for 
a  study  of  the  details  of  deveU)pment  and  spoi'e  formation  and  the 
relation  of  the  foot  to  the  tissue  at  the  base  of  the  archegonium. 

Reference.    Campbell,  23. 

Questions.  What  are  the  advantages  in  the  form  and  position 
of  the  thallus  of  Marchantia  ?  What  are  its  life  habits  ? 
What  are  probably  its  most  effective  means  of  multiplica- 
tion ?  What  great  advance  in  structure  is  presented  by  the 
sexual  organs  over  those  of  the  algse  generally  ?  Under 
what  conditions  are  the  sperms  set  free  and  the  eggs  ferti- 
lized ?  W^hat  new  features  are  introduced  by  the  develop- 
ment of  the  Q^g  after  fertilization,  —  features  not  generally 
present  in  the  algie?  Are  there  spores  among  the  alga^ 
comparable  to  the  spores  of  Marchantia  ?  Is  it  a  new  type 
of  spore  in  plant  evolution  ?  Describe  the  life  history  and 
distinguish  between  the  sexual  phase,  or  gametophyte,  and 
the  asexual  phase,  or  sporophyte.  What  is  the  physiological 
relation  of  the  sporophyte  to  the  gametophyte  ?  Draw  and 
arrange  a  series  of  diagrams  illustrating  the  chief  stages 
throughout  the  life  history,  using  two  colored  pencils  to 
designate  gametophytic  and  sporophytic  phases  respectively 
(App.  18).  Construct  a  life-history  formula  which  will  ex- 
press   this  succession  (App.  18). 

125.  Porella,  a  leafy  liverwort.  Frullania,  Eadula,  or  other  types  may  also 
be  studied  by  a  similar  outline.  Examine  living  material  and  describe  the 
life  habits.    Note  the  dying  away  of  older  parts  of  the  plants. 

A.  General  morphology.  Study  and  compare  the  two  surfaces  of  the 
plants. 

1.  Draw  the  upper  surface.  Note  the  stem  bearing  two  rows  of  over- 
lapping leaf-like  scales,  generally  called  leaves,  at  the  side.  Is  the 
branching  regular?  Observe  the  bud-like  structure  of  the  gruiu- 
ing  point. 

2.  Draw  the  lower  surface.  Note  the  third  row  of  small  scales  or 
leaves  (amphigastria)  somewhat  irregularly  distributed  along  the 
stem  ;  also  show  the  under  side  of  the  lateral  rows.  Searcii  for 
rhizoids. 


124  TYPE  STUJ)TES 

B.  VegetatAve  structure. 

1.  Mount  some  of  the  leaves  in  water.  Note  the  simple  cell  structure. 
Are  these  leaf -like  scales  related,  that  is,  homologous,  to  the  leaves 
of  ferns  and  seed  plants  ?  Draw  a  portion  of  the  leaf  and  show 
details  of  cell  structure,  arrangement  of  chloroplasts,  etc. 

2.  Examine  the  rhizoids,  if  found,  and  compare  with  those  of  Mar- 
chantia.    Draw. 

3.  Lengthwise  microtome  sections  of  the  growing  points  will  show  the 
method  of  growth  from  an  apical  cell  and  the  development  of  the 
leaves. 

C.  The  antheridia,  or  male  sexual  organs.  These  are  found  in  Porella  on 
small  special  branches  at  the  side  of  the  stem  near  the  tip  of  the  plant. 
Draw  an  antheridial  branch  or  group  of  branches. 

1.  Tease  the  leaves  of  an  antheridial  branch  apart,  under  a  dissecting 
microscope  if  possible,  and  find  the  antheridia.  How  are  they  borne 
with  reference  to  the  stem  and  leaves  ?  Show  their  position  in  a 
diagram, 

2.  Draw  an  antheridium,  noting  the  long  stalk  and  the  sperm  case. 
Crush  older  antheridia  and  observe  the  contents  with  developing 
sperms;  stain  with  iodine. 

3.  Lengthwise  microtome  sections  of  the  antheridiaLbranches  (Sec.  212) 
show  clearly  the  cell  structure  of  the  antheridia  and  their  develop- 
ment, and  also  the  development  of  the  sperms. 

D.  The  archegonia,  or  female  sexual  organs.  Search  plants,  not  bearing 
antheridia,  for  short  lateral  branches  in  which  the  rather  large  leaves 
form  close  tufts.  These  are  archegonial  branches.  The  sexual  organs 
of  Porella  are  therefore  on  separate  plants,  male  and  female,  and  the 
genus  is  therefore  dioecious. 

1.  Dissect  these  branches  carefully  and  note  a  sac-like  envelope  (peri- 
anth) around  a  terminal  group  of  archegonla.  Diagram  their  position. 

2.  Tease  the  archegonia  free  from  the  surrounding  leaves  and  envelope 
and  draw  one  or  more.  Note  their  form  in  comparison  with  the 
archegonia  of  Marchantia. 

3.  It  will  frequently  be  found  that  one  of  the  archegonia  has  been 
fertilized  and  that  a  young  sporophyte  is  present  in  its  much  en- 
larged base,  now  called  the  calyptra. 

E.  The  sporophyte.  Old  sporophytes,  also  called  fruits,  may  be  found  at 
the  tips  of  old  archegonial  branches.  Dissect  away  the  leaves  and 
envelope  around  the  base.    Note  : 

1.  The  relatively  long  stalk  attached  to  the  tip  of  the  sexual  plant 
(gametophyte)  by  ?(,foot. 

2.  The  terminal  spore  case  generally  split  lengthwise  into  four  parts. 


ANTHOCEROS  125 

3.  Spores  and  elaters  frequently  held  within  the  split  spore  case.  Draw 
a  sporophyte  and  details  of  the  spores  and  elaters. 

4,  Lengthwise  microtome  sections  of  archegonial  branches  (Sec.  212) 
give  extremely  interesting  slides  of  various  stages  in  the  development 
of  the  sporophytes,  showing  the  foot  and  details  of  the  spore  case 
when  the  latter  is  still  contained  within  the  archegonium  (see  Prin- 
ciples, Fig.  256).  Note  the  f  our-lobed  spore  mother  cells,  or  the  groups 
of  four  spores,  tetrads,  produced  by  them.  Compare  this  sporophyte 
with  that  of  Marchantia.    Draw  its  characteristic  features  in  detail. 

Reference.     Campbell,  23. 

126.  Anthoceros,  the  horned  livenvort.  This  type  is  chiefly  interesting  for 
the  sporophyte. 

A.  The  sexual  plants,  or  gametophytes.  Note  the  relatively  small  thallus, 
lobed  but  unbranched  and  with  an  irregular  margin.  Contrast  its  sim- 
plicity with  the  gametophytes  of  Marchantia  and  Porella.  Make  a 
habit  sketch  to  show  these  points,  together  with  the  elongated  sporo- 
phytes which  rise  from  the  thallus. 

1.  The  vegetative  structure  may  be  studied  from  cross  sections  cut  in 
pith.  Observe  the  simple  cell  structure,  each  cell  containing  a 
single  large  chromatophore.  Note  the  cavities  on  the  lower  side  gen- 
erally containing  colonies  of  the  blue-green  alga,  Nostoc. 

2.  The  sexual  organs  are  best  examined  from  microtome  sections  and 
form  a  detailed  study. 

B.  The  sporophyte.  Observe  the  sporophytes  of  various  ages  developing 
upon  the  gametophyte,  rising  out  of  cylindrical  collar-like  outgrowths 
of  the  gametophytes. 

1.  Study  and  draw  the  oldest  sporophytes,  noting  how  they  split  into 
two  parts,  which  separate,  and  the  delicate  thread  of  shriveled 
sterile  tissue  (columella)  which  rises  between.  Pick  such  a  sporo- 
phyte off  and  mount  entire.  Where  are  the  ripe  spores  formed  ? 
Examine  the  surface  for  pores,  or  stomata,  with  guard  cells. 

2.  Lengthwise  microtome  sections  of  the  sporophytes  (Sec.  212)  in- 
cluding portions  of  the  thallus  will  show  the  remarkable /oo^,  region 
of  growth,  and  the  cylinder  of  spore-producing  tisvsue  (archesporium). 
with  stages  in  the  development  of  the  spores  and  other  details  of 
cell  structure  of  great  interest  (see  Principles,  Fig.  258). 

This  sporophyte  is.  the  most  interesting  of  any  in  the  liverworts  because 
of  a  number  of  features  suggestive  of  life  habits  in  higher  plants.  Chief 
among  these  are  the  stomata,  the  long  period  of  growth  and  fructification, 
and  the  large  foot  drawing  water  from  the  gametophyte. 

Keirren<  K.    Campbell,  23. 


126  TYPE   STUDIES 


THE  MOSSES,  OR  MUSCI 

127.  Sphagnum,  the  peat  moss.  Study  the  life  habits,  tufted  growth,  and 
ability  to  absorb  water.  Explain  the  latter  property  after  a  study  of  the 
cell  structure. 

A.  General  morphology.    Note  : 

1.  The  main  stem. 

2.  The  lateral  branches.  Compare  their  arrangement  at  the  top  of  the 
stem  and  below  in  a  species  that  grows  up  into  the  air.  What  two 
forms  of  branches  are  present  and  what  are  the  factors  that  deter- 
mine their  direction  of  growth  ? 

3.  The  leaf-like  scales  or  leaves. 
Illustrate  these  points  in  a  habit  sketch. 

B.  Vegetative  structure.  Tease  out  the  tip  of  a  branch  and  obtain  the 
youngest  leaves  possible.  Compare  their  structure  with  that  of  the 
mature  leaf.  Make  a  series  of  drawings  under  h.p.,  showing  this  cell 
structure  in  young  and  old  leaves.    They  should  make  clear  : 

1.  The  significance  of  the  large  empty  cells,  tracheids,  found  in  the 
older  leaf-like  scales.  What  is  the  structure  of  these  cells  with 
their  rib-like  thickenings  and  large  circular  openings'?  Trace  their 
development  from  the  cells  of  young  scales. 

2.  The  structure  of  the  green  framework  which  surrounds  the  empty 
cells  in  old  leaves.  Of  what  is  the  framework  composed  ?  Trace 
its  development  from  the  cells  of  young  scales. 

3.  Examine  the  cell  structure  of  the  stem.  Are  empty  cells,  tracheids, 
found  there  ? 

C.  The  sexual  organs,  antheridia  and  archegonia.  These  are  so  rarely 
found,  since  they  are  generally  formed  early  in  the  spring  or  late  in 
winter,  that  their  study  is  not  practicable  in  a  general  course. 

1).  The  sporophyte.  Note  the  groups  of  sporophytes,  also  called  fruits  of 
the  moss,  situated  at  the  tips  of  the  tufted  branches.  Make  a  habit 
sketch.    Study  : 

1.  The  large  globular  spore  case,  opening  by  a  lid,  and  situated  at  the 
end  of  a  rather  thick  column  (pseudopodium). 

2,  Lengthwise  sections  will  show  that  the  column  is  not  a  part  of  the 
sporophyte  but  an  outgrowth  from  the  gametophyte.  The  sporo- 
phytes  have  no  stalk  but  are  attached  to  the  column  by  a  large  foot 
(see  Principles,  Fig.  260,  B).  The  spores  are  developed  in  a  dome- 
shaped  spore-producing  tissue  (archesporium).  Draw  characteristic 
features  of  the  sporophyte  in  detail. 

Reference.    Campbell,  23. 


THE   MOSS  127 

128.  Funaria,  Mnium,  Atrichum,  or  other  common  moss.*  *  Poly- 
trichum  has  some  advantages  as  a  type  on  account  of  its  size, 
but  the  life  history  of  a  moss  is  more  easily  studied  from  some 
of  the  smaller  forms.  Study  the  life  habits  of  the  type  examined 
and  of  such  other  forms  as  may  be  available  (App.  19). 

A.  The  leafy  moss  plant.    Note  : 

1.  The  stem,  bearing  leaf -like  scales  generally  called  leaves. 
What  is  their  arrangement  around  the  stem  ? 

2.  Rhizoids  attaching  the  base  of  the  plant  to  the  substratum. 

3.  The  long-stalked  sporophyte^  also  called  the  fruit  of  the 
moss,  arising  from  the  tip  of  the  moss  plant  and  terminat- 
ing in  the  large  swollen  spore  case.  If  the  spore  case  is 
mature,  cut  it  open  to  obtain  the  spores,  or,  if  open,  shake 
out  the  spores. 

Show  the  above-given  points  in  a  habit  sketch. 

B.  The  protonema  and  rhizoids.  Carefully  wash  away  the 
earth  around  the  base  of  a  moss  plant  in  a  watch  glass  of 
water  and  mount  it  with  any  accompanying  green  filamentous 
growth.    Examine  under  m.p. 

1.  Note  the  filaments,  green  and  brown,  attached  to  the  base 
of  the  moss  plant.  The  brown  filaments  are  called  rhizoids 
and  were  once  green,  but  the  cells  have  largely  lost  their 
protoplasmic  contents  and  the  cell  walls  have  become 
brown.  The  green  filaments  have  the  same  structure  as 
other  green  filaments,  which  are  to  be  found  growing 
freely  over  the  substratum.  They  really  form  a  part  of 
what  is  called  the  p^rotonema. 

2.  The  protonema  first  arose  from  the  germination  of  spores 
developed  in  the  spore  cases  of  sporophytes,  but  additional 
protonema  may  be  developed  from  the  base  of  the  moss 
plants.  Draw  the  green  and  brown  filaments  under  h.p., 
comparing  their  cell  structure  carefully. 

3.  Search  for  small  buds  which  develop  on  the  protonema 
and  grow  into  the  leafy  moss  plants.  Draw  stages  in  their 
development  if  possible. 


128  TYPE  STUDIES 

4.  Cultures  of  moss  spores  sown  on  earth  (Sec.  206)  will  give  a  thick 
growth  of  protonema  which,  when  examined  at  the  proper  stage, 
will  show  abundant  buds  and  young  leafy  moss  plants. 

C.  Vegetative  structure  of  the  leafy  moss  plant. 

1.  Mount  a  single  leaf  and  examine  under  ni.p.  Note  the 
line  of  elongated  cells  in  the  middle  region,  constituting 
a  simple  midrib,  and  the  simple  cell  structure  of  the  ex- 
panded portions  on  either  side.  Show  these  points  in  an 
outline  sketch. 

2.  Examine  a  group  of  cells,  if  not  previously  studied 
(Sec.  62),  for  the  details  of  cell  structure,  chloroplasts, 
nucleus,  etc. 

D.  The  leafy  moss  plants  bearing  sexual  organs.  The  sexual 
organs  may  be  found  on  separate  moss  stems,  and  such 
mosses  have  consequently  been  called  dicecious.  However, 
in  some  species  the  male  and  female  stems  have  been  found 
to  be  joined  at  the  base,  so  that  they  are  really  branches  of 
the  same  plant,  which  is  consequently  monoecious.  Male  and 
female  stems  may  also  arise  from  the  same  protonema. 

1.  The  antheridial,  or  male,  stems.  These  are  generally 
smaller  than  the  female,  and  the  leaves  at  the  top  of  the 
stem  form  an  expanded  rosette  surrounding  the  cluster  of 
antheridia.  Note  the  color  of  the  cluster  of  antheridia 
and  their  surrounding  leaves.  Draw  an  antheridial  stem 
to  show  these  points. 

2.  The  archegonial,  or  female,  stems.  These  are  generally 
larger  than  the  antheridial  stems,  and  the  leaves  at  the 
top  are  closely  rolled  around  one  another.  Search  for 
such  stems  in  a  mat  of  mosses  bearing  mature  antheridial 
stems.  Tease  the  leaves  apart  carefully  at  the  tip  under 
a  dissecting  microscope,  thus  exposing  the  group  of  arche- 
gonia.  Make  a  semidiagrammatic  sketch  of  the  tip  of  the 
plant,  showing  the  relation  of  parts. 

E.  The  antheridia,  or  male  sexual  organs.  Tease  a  cluster  of 
antheridia  apart  and  mount.    Note  : 


THE  MOSS 


129 


1.  The  antheridia,  elliptical,  cellular  structures  with  short 
stalks.  The  upper  part  is  a  sperm  case  and  opens  at  the 
end  by  the  swelling  and  rupture  of  a  special  group  of  cells. 
Draw  a  mature  antheridium  and  then  crush,  if  possible, 
to  study  its  contents  of  developing  sperms.  Stain  the 
crushed  preparation  with  iodine,  which  may  show  some 
details  of  the  structure  of  the  sperms. 

2.  Cxreen  filaments,  paraphyses,  among  the  antheridia  and 
rising  above  them.  Observe  the  form  and  contents  of  the 
cells  and  draw. 

Make  a  semidiagrammatic  sketch  of  how  a  lengthwise  sec- 
tion of  the  tip  of  an  antheridial  plant  would  appear,  using 
prepared  slides  when  possible,  as  described  in  3. 

3.  Lengthwise  microtome  sections  of  the  tips  of  antheridial  plants 
(Sec.  212)  present  stages  in  the  development  of  the  antheridia 
and  details  of  their  cell  structure  and  the  development  of  the 
sperms. 

F.  The  archegonia,  or  female  sexual  organs.  Tease  apart  the 
enveloping  leaves  around  the  end  of  an  archegonial  plant 
Note  : 

1.  The  stalked  archegonia  with  very  long  necks.  Older 
stages  will  show  the  necks  open  above  and  the  eggs  in  the 
swollen  bases.  Younger  stages  will  show  unopened  necks 
with  the  row  of  canal  cells.    Draw. 

2.  Delicate  filaments,  paraphyses,  among  the  archegonia. 

^  Make  a  semidiagrammatic  sketch  of  how  a  lengthwise  sec- 
tion of  the  tip  of  an  archegonial  plant  would  appear,  using 
prepared  slides  if  possible,  as  described  in  3. 

3.  Lengthwise  microtome  sections  of  the  tips  of  archegonial  plants 
(Sec.  212)  present  details  of  the  structure  and  development  of  the 
archegonia  and  frequently  of  the  young  sporophytes. 

G.  The  development  of  the  sporophyte.  Study  material  in 
which  developing  sporophytes  are  still  contained  within 
the  enlarged  sac-like  archegonium,  now  called  the  calyptra. 
Split  the  calyptra  with  a  point  of  a  needle  and  remove  it  from 
the  needle-shaped  sporophyte.    Pick  the  young  sporophyte 


130  TYPE  STUDIES 

off  from  the  leafy  moss  plant,  or  gametophijte,  and  mount 
entire.    Note  and  draw  : 

1.  The  foot  at  the  base  of  the  sporophyte  which  was  im- 
bedded in  the  tissue  of  the  gametophyte. 

2.  The  growing  point  at  the  tip  of  the  sporophyte.  The 
sporophyte  should  be  turned  on  the  slide  so  that  the 
growing  point  under  h.p.  shows  the  large,  wedge-shaped 
apical  cell  and  the  series  of  segments  which  are  cut  off 
from  it  on  either  side. 

H.  The  adult  sporophyte.  In  a  habit  sketch,  if  not  previ- 
ously drawn,  show  the  relation  of  the  sporophyte  to  the 
gametophyte,  its  long  stalk,  and  the  spor^e  case  bearing  the 
calyptra  like  a  cap  at  the  end.  Select  a  sporophyte  in 
which  the  spore  case  is  still  unopened  and  covered  by  the 
calyptra. 

1.  Remove  the  calyptra  and  under  a  hand  lens  note  the 
cover,  or  operculum,  over  the  cavity  of  the  spore  case  and 
the  position  of  a  ring,  generally  present  just  below  the 
cover. ^    Draw. 

2.  Pick  off  the  cover  and  ring.  Mount  in  water  and  draw. 
Note  the  cell  structure  of  the  ring  and  its  behavior 
when  wet. 

3.  With  a  razor  cut  off  the  end  of  the  sporophyte  after 
the  cover  has  been  removed  and  mount  in  water.  A 
circle  of  teeth  is  generally  evident  in  the  preparation, 
all  pointing  inward  in  a  regular  arrangement.  Under- 
neath the  teeth  may  frequently  be  found  another  circle 
of  delicate  segments  similar  in  form  and  arrangement  to 
the  teeth.  Count  the  teeth  and  segments.  Show  these 
points  in  a  figure.  Note  the  sjyores  in  the  spore  case. 
The  circles  of  teeth  and  segments  constitute  the  peristome. 
If  the  teeth  are  not  clearly  shown,  examine  material  as 
described  in  4. 

1  Species  of  Bnpim  are  especially  favorable  for  the  study  of  the  ring  and 
peristome  (see  Principles,  Fig.  269) . 


thp:  moss  131 

4.  Select  an  old  sporophyte  in  Avhich  the  spore  case  has 
ripened  and  is  open.  Carefully  split  it  lengthwise  with  a 
needle,  after  soaking  in  hot  water  or  a  dilute  potash  solu- 
tion, or  mount  entire.  Note  the  circle  of  teeth  and  cilia 
around  the  opening,  and  the  spores  generally  present. 
Draw  these  structures. 
I.  The  structure  of  the  spore  case.  Make  lengthwise  sections 
in  pith  of  the  unopened  spore  case. 

1.  Slices  from  the  surface  rather  low  down  on  the  spore 
case  are  likely  to  give  surface  views  showing  pores,  or 
stomata,  with  two  guard  cells.  Draw.  Compare  these 
structures  with  stomata  which  may  have  been  studied  on 
the  leaves  of  seed  plants. 

2.  Median  sections  present  a  cylinder  of  spore-producing 
tissue  (archesporium)  inclosing  a  large  pith-like  region,  or 
columella.  A  large  air  space  crossed  by  filaments  lies 
between  the  tissue  in  the  interior  of  the  spore  case  and 
the  outer  wall  (see  Principles,  Fig.  270,  U). 

Show  the  structure  of  the  median  section  in  a  semi- 
diagrammatic  figure. 

3.  The^  histology  of  the  spore  case  can  best  be  studied  in  lengthwise 
microtome  sections. 

Reference.    Campbell,  23. 

Questions.  What  are  the  life  habits  of  the  mosses  ?  Why  do 
they  so  frequently  grow  together  in  large  tufts  or  mats,  and 
what  are  the  advantages  of  these  growth  habits  ?  What  are 
the  advantages  of  their  erect  stems  and  the  arrangement  of 
the  leaf-like  scales  ?  What  are  the  means  of  multiplication  ? 
What  great  advances  in  structure  are  shown  by  the  sexual 
organs  over  those  of  the  algas  ?  Under  what  life  conditions 
are  the  sperms  set  free  and  the  eggs  fertilized  ?  Trace  the 
development  of  the  egg  after  fertilization  into  the  stalked 
structure  bearing  the  spore  case.  Why  is  this  structure  con- 
sidered an  asexual  generation  (sporophyte)  distinct  from  a 


132  TYPE   STUDIES 

sexual  generation  (gametophyte)  ?  Are  there  spores  among 
the  algae  comparable  to  the  moss  spores  ?  Is  it  a  new  type 
of  spore  in  plant  evolution  ?  What  is  the  physiological  rela- 
tion of  the  sporophyte  to  the  gametophyte  ?  What  impor- 
tant advance  in  the  structure  of  the  moss  sporophyte  over 
that  of  Marchantla  is  indicated  by  the  presence  of  stomata  ? 
In  what  other  respects  does  the  moss  sporophyte  show  ad- 
vances over  that  of  Marchantia  ?  Describe  the  life  history, 
distinguishing  between  the  sexual  phase,  gametophyte,  and 
the  asexual  phase,  sporophyte.  Draw  and  arrange  a  series 
of  diagrams  illustrating  the  chief  stages  throughout  the  life 
history,  using  two  colored  pencils  to  designate  the  gameto- 
phytic  and  sporophytic  generations  respectively  (App.  18). 
Construct  a  life-history  formula  that  will  express  this  suc- 
cession (App.  18). 

THE  FERNS,  OE  FILICINEiE 

129.  Field  work  on  the  ferns,  horsetails,  club  mosses,  and  quillworts.  Repre- 
sentatives of  these  groups  have  well-defined  habits,  some  living  under  very 
special  life  conditions  and  others  forming  striking  and  characteristic  associ- 
ations (see  Principles,  p.  475),  such  as  the  growths  of  bracken  fern  {Pteris  aqui- 
lina),  many  horsetails,  and  some  club  mosses  and  quillworts.  These  may  be 
studied  in  the  field  and  the  habits  of  growth  and  life  conditions  noted.  The 
adaptations  of  the  pteridophytes  are  extremely  various.  There  are  hydro- 
phytes, as  some  species  of  Marsilia  and  Isoetes,  and  floating  aquatics,  such  as 
Azolla  and  Salvinia.  Numerous  mesophytes  occur  especially  among  the 
ferns,  as  illustrated  by  species  of  Aspidium,  Asplenium,  and  Cystopteris. 
Xerophytes  are  represented  in  the  ferns  by  such  forms  as  Gymnogramme  in 
the  far  Southwest  and  Polypodium  incanum  in  the  South.  Equisetum  and 
certain  species  of  Selaginella  are  excellent  types  of  xerophytes,  and  some 
species  of  the  latter  may  remain  perfectly  diy  for  long  periods  and  will  re- 
vive again  when  wet.  Field  work  on  the  pteridophytes  should  be  planned 
with  reference  to  the  ecological  relations  of  the  forms  and  may  be  accom- 
panied with  great  advantage  by  moi-phological  and  histological  studies  that 
will  show  the  character  of  the  adaptations  in  the  plant's  structure.  In  tak- 
ing up  the  pteridophytes  the  student  pa.sses  to  a  group  whose  life  relations 
approach  those  of  the  seed  plants,  and  they  may  be  studied  in  the  field  largely 
after  the  same  methods  as  the  latter  group  (see  Sec.  157).    The  displays 


'JlIK   FKllN  133 

offered  in  park  greenhouses  and  conservatories  present  excellent  <jpportii- 
nities  to  city  classes  for  interesting  studies  on  life  habits,  especially  of 
tropical  forms. 

130.  Aspidium,  Pteris,  Adiantum,  or  other  common  fern.*  *  There 
are  a  number  of  wild  and  greenhouse  ferns,  all  almost  equally 
good  for  a  type  study  (App.  20).  Examine  the  growing  fern  : 
(1)  determine  the  position  of  the  stem,  its  habits  of  growth, 
whether  upright  or  creeping,  partly  above  ground,  or  wholly  sub- 
terranean ;  (2)  examine  the  arrangement  and  distribution  of  the 
fronds  or  leaves,  their  manner  of  unrolling ;  (8)  study  fruiting 
fronds  bearing  on  their  surface  minute  brown  sporangia,  variously 
arranged  and  protected  in  different  species  of  ferns. 

A.    General  morijhology.    Kote  : 

1.  Thes/'e/?!,  if  creeping  called  a  rootstock  (rhizome).  Observe 
whether  it  is  subterranean  or  above  ground. 

2.  The  roots,  their  distribution  on  the  stem. 

3.  The  fronds,  or  leaves,  consisting  of  a  leafstalk  (stipe) 
and  blade  (lamina).  Note  the  unrolling  of  the  fronds. 
Search  for  the  scars  of  old  fronds  formerly  on  the 
stem.  The  fronds  of  most  ferns  are  compound,  tliat  is, 
divided  into  segments  or  leaflets.  Sometimes  the  primary 
segments  are  divided  again  and  these  still  again.  Such 
fronds  are  twice  or  thrice  compound  or  branched  as  the 
case  may  be.  Describe  the  conditions  in  the  frond  of  your 
type.  Examine  the  veins  in  the  leaves  and  describe  their 
branching.  Has  the  system  of  venation  any  relation  to 
the  form  of  the  margin  or  the  compound  character  of 
the  frond? 

4.  The  sjjorangia  on  the  surface  of  the  leaves.  Observe 
their  arrangement  in  spots  or  regions.  Each  spot  is 
called  a  sorus  and  is  generally  partly  or  wholly  covered 
by  a  protective  membrane,  the  indusium.  Do  the  posi- 
tions of  the  sori  bear  any  relation  to  the  veins  ?  The 
structure  and  position  of  the  indusium  is  an  important 
character  in  the  classification  of  ferns. 


134  TYPE  STUDIES 

Illustrate    in    a    habit    sketch    the    characteristic    features 

of  frond   and   stem,  and  draw  in  detail  a  portion  of  a 

fruiting  frond,  showing  the  venation  and  distribution  of 

sporangia. 

B.   The  sporangia.    Scrape  off  some  of  the  sporangia  from  a 

sorus  and  mount  in  water.    Draw  under  h.p.  a  side  view  of 

a  sporangium  from  which  the  spores  have  been  discharged. 

Note  and  show  in  the  figure : 

1.  The  stalk. 

2.  The  flattened  spore  case  consisting  of  thin-walled  tissue 
except  for  a  row  of  thick-walled  cells  along  the  margin, 
forming  the  ring  (annulus).  Note  the  extent  of  the  ring 
and  the  position  of  the  thickened  portions  of  its  walls. 

3.  The  wide  rent  in  old  and  empty  sporangia  opposite 
the  ring. 

4.  Sp>ores  free  or  inclosed  in  the  sporangia.    Draw  in  detail. 

5.  Soak  some  ripe,  unopened  sporangia  in  water  and  place 
on  a  slide  without  a  cover  glass.  Watch  them  under 
l.p.  as  they  become  dry.  Explain  from  the  movements 
of  the  ring  how  the  sporangium  opens  and  discharges 
its  spores. 

The  fact  that  the  fern  plant  has  no  sexual  ol-gans  but  produces 
instead  asexual  spores,  and  that  it  alternates  with  a  sexual  genera- 
tion (as  will  appear  later),  makes  it  a  sporophyte.  The  details  of 
spore  formation  show  that  the  spores  are  comparable  to  those  of 
the  bryophytes. 

G.  The  details  of  the  development  of  the  sporangia  and  of  spore  forma- 
tion can  best  be  studied  from  microtome  sections  through  the  sori. 
Species  of  Aspidium  are  especially  favorable  for  this  study  (Sec.  212). 
Follow  stages  as  outlined  in  Goehel,  10,  Fig.  165.    Note  that  the  spores, 
sixty-four  in  number,  are  developed  in  groups  of  fours,  tetrads,  in 
spore  mother  cells. 
C.   The  cell  structure,  or  histology,  of  the  stem.    The  fern  is 
not  a  favorable  subject  for  a  detailed  study  of  the  tissues 
characteristic  of  higher  plants,  but  certain  peculiarities  are 
important. 


THE   FERN  135 

1.  In  cross  sections  of  the  stems  or  leafstalks  note  the 
fibrn-vascular  hvndies  and  regions  of  thick-walled  rifjid 
tissue  (sclerenchyma)  differentiated  from  the  thin-walled 
fundamental  or  (/round  tissue  (parenchyma).  Show  their 
distribution  in  an  outline  drawing.  The  outer  layer  of 
cells  will  be  clearly  differentiated  as  an  epidermis  if  the 
structure  studied  is  aerial, — that  is,  above  ground.  Why  ? 
What  is  the  chief  purpose  of  the  rigid  tissue  ?  What  are 
some  of  the  functions  of  the  fibro- vascular  bundles  ? 

2.  In   cross  sections   of   fibro-vascular  bundles,  under  li.p.,  observe 

(1)  large,  thick-walled,  empty  cells,  called  tracheids;  these  with 
small,  thick-walled  cells  in  the  interior  constitute  the  wood,  or  xylem ; 

(2)  the  surrounding  soft,  thin-walled  tissue,  called  bast,  or  phloem, 
containing  sieve  tubes  (see  Princij)les,  Fig.  274);  (.3)  the  bundle  sheath 
and  phloem  sheath,  two  adjacent  cell  membranes  inclosing  the  bast 
and  wood. 

Study  these  elements  of  the  bundle  in  stained  preparations  (Sec. 
212)  of  cross  and  lengthwise  sections,  making  detailed  drawings. 

J).   The  cell  structure,  or  histology,  of  the  frond. 

1.  Strip  off  the  epidermis  from  the  lower  surface  of  the 
frond  and  mount  in  water,  with  the  outer  surface  of  the 
epidermis  uppermost  on  the  slide.  Note  the  pores,  or  sto- 
mata,  with  their  guard  cells,  and  draw^  these  with  adjacent 
epidermal  cells. 

2.  Strip  off  epidermis  from  the  upper  surface.  Has  it 
stomata  ? 

8.  Sections  of  the  blade  will  show  the  green  parenchyma, 
mesophyll,  and  air  spaces  within  the  leaf  opposite  the 
stomata.  The  cells  of  the  green  tissue  on  the  upper  side 
of  the  frond  are  usually  arranged  in  a  firm  layer,  ov  pali- 
sade. Note  that  the  veins  are  fibro-vascular  bundles  giving 
strength  to  the  expanded  blade,  besides  carrying  water  to 
all  parts  of  it. 

E.  The  structure  of  the  root  tip.  Study  lengthwise  microtome  sections  of 
the  root  tip  (Sec.  212).  Note  the  root  cap  over  the  growing  j>oint,  which 
consists  of  a  pyramidal  apical  cell  whose  apex  points  inwards.  Segments 


136  TYPE   STUDIES 

are  cut  off  from  the  sides  of  the  apical  cell  to  form  the  root  and  from 
its  base  to  form  the  root  cap.  Trace  the  history  of  these  segments  in 
your  preparation.    Draw. 

F.  The  (jermmation  of  the  sjwres.  Examine  a  two-  or  three- 
weeks-old  culture  of  fern  spores  sown  on  earth  or  on  old, 
dirty  flowerpots  (Sec.  208).  Spores  are  to  be  found  in  vari- 
ous stages  of  germination.  The  structure  developed  from 
the  spore  is  called  a  prothalUum.  It  will,  however,  become 
apparent  from  the  study  of  a  mature  prothallium  that  the 
structure  is  a  gametophyte.    Note  : 

1.  The  ruptured  spore  and  protruding  green  filament. 

2.  The  change  of  the  tip  of  the  filament  into  a  flat  plate  of 
cells  by  the  formation  of  oblique  walls,  which  cut  out  a 
wedged-shaped  apical  cell. 

3.  The  development  of  rh  Izoids.    Where  ? 

4.  As  development  proceeds  the  apical  cell  becomes  situated 
in  a  notch  on  account  of  the  growth  of  the  cells  on  both 
sides,  and  the  prothallium  takes  a  heart-shaped  form. 

Draw  a  series  of  stages  in  the  germination  of  the  spores 
and  development  of  the  prothallia. 

G.  The  mature  prothallia,  or  gametophytes.  Examine  a  large, 
heart-shaped  prothallium  six  or  more  weeks  old.  Observe  its 
thalloid  structure,  the  angle  at  which  it  rises  from  the  sub- 
stratum, the  position  of  the  notch.  Mount  with  the  lower 
side  uppermost.    Note : 

1.  The  position  of  the  rhizoids. 

2.  Small,  round  antheridia,  many  of  them  probably  open 
and  brownish,  situated  at  the  lower  or  posterior  end  of 
the  prothallium. 

3.  The  projecting  necks  of  archegonia  just  back  of  the  notch 
on  a  thicker  region  of  the  prothallium  called  the  cushion. 

Show  the  position  of  these  structures  in  an  outline  sketch. 
The  prothallia  are  gametophytes,  since  they  produce  sexual 
organs,  arise  from  the  asexual  spores  of  the  sporophytes  (fern 
plants),  and  alternate  with  this  asexual  generation. 


THE   FERN  X37 

H.  The  antherldia,  or  male  sexual  orr/aiis.  These  are  fre- 
quently more  easily  studied  on  smaller  dwarf  prothallia, 
especially  those  which  have  been  growing  crowded  together' 
and  are  consequently  irregularly  developed  and  devoted  en- 
tirely to  the  production  of  antheridia  (not  a  strictly  normal 
condition).  Examine  under  h.p.  mature  antheridia  situated 
near  the  edge  of  the  prothallium,  so  that  they  may  be  seen 
in  side  view.    Note  and  illustrate  in  figures  : 

1.  The  funnel-shaped  basal  cell. 

2.  The  ring  cell  surrounding  the  side  of  the  antheridium. 

3.  The  disk-shaped  cover  cell. 

4.  The  central  group  of  developing  sperms,  or  sperm  mother 
cells. 

5.  Mature  antheridia,  especially  those  borne  on  somewhat 
dry  prothallia,  when  mounted  in  water,  will  open  and 
discharge  the  sperms.  Watch  their  escape  and  movements 
and  then  stain  with  iodine. 

6.  Observe  the  coiled,  spiral  bodij  of  the  sperm,  the  numerous 
cilia  at  the  pointed  end,  and  generally  a  vesicle,  the  remains 
of  the  sperm  mother  cell,  at  the  larger  end. 

I.  The  archegonla,  or  female  sexual  organs.    Mount  a  large, 
heart-shaped  prothallium  with    the   lower  side    uppermost,' 
together  with  several  dwarf  prothallia,  some  of  whose  an- 
theridia are  likely  to  discharge  sperms.    Study  the  necks 
of  the  archegonia  projecting  from  the  cushion  back  of  the 
notch.    Note  how  they  curve  backward  and  do^\Tiward  from 
the  cushion.    Some  of  the  necks  are  likely  to  open.    Observe 
that  sperms  swimming  freely  in  the  water  gather  around 
the  open  necks  and  enter  them.    Illustrate  these  features. 
1.  The  structure  of  the  archegonium  can  best  be  studied  froui  mici-o- 
tome  sections  cut  lengthwise  of  the  prothallium  (Sec.  212).    The 
base  of  the  archegonium  with  the  egg  lies  imbedded  in  the  prothal- 
lium.   There  are  only  two  or  three  canal  cells. 
J.   The    young   sporophytes.      In    cultures    of    prothallia   two 
or    three   months    old,    which    have     been    watered    from 


138  TYPE   STUDIES 

above,  observe  the  development  of  young  fern  j^lants,  or 
sporophytes.  Note  the  position  of  the  small  first  leaf 
rising  generally  through  the  notch  of  the  prothallium. 
Kemove  such  a  young  sporophyte  with  the  attached  pro- 
thallium,  wash  the  dirt  from  the  root,  and  draw  under 
low  magnification. 

1.  The  development  of  the  sporophyte  can  best  be  studied  from  micro- 
tome sections  of  material  cut  as  described  in  I,  1,  Younger  stages 
show  the  early  divisions  of  the  egg  into  four  regions  which  develop 
respectively  into  a  stem,  root,  first  leaf,  and  large  foot  attaching  the 
young  sporophyte  to  the  gametophyte.  Later  stages  will  show  the 
gradual  differentiation  of  these  four  regions  into  the  organs  named 
above.  The  large  foot  brings  the  sporophyte  into  intimate  physio- 
logical relations  with  the  gametophyte  (see  Principles,  Fig.  279,  A), 
from  which  it  may  obtain  food  until  able  to  live  independently 
by  the  development  of  a  root-and-leaf  system. 

References.  Campbell,  23 ;  and  for  a  detailed  study  of  the 
structure  and  life  history  of  Pterls  aqulllna,  see  Sedgwick 
and  Wilson,  An  Introduction  to  General  Biology,  1895. 

QuESTioxs.  What  are  the  growth  habits  of  the  ferns  ?  Are 
they  long-lived  ?  What  are  the  means  of  reproduction  ? 
Are  there  other  means  besides  spores  ?  Why  are  the  spores 
of  ferns  and  bryophytes  comparable  to  one  another  ?  Trace 
the  history  of  the  germination  of  fern  spores.  Are  the  pro- 
thallia  generally  long-lived  ?  Why  are  they  gametophytes  ? 
Are  the  gametophyte  and  sexual  organs  simpler  in  struc- 
ture than  those  of  the  mosses  and  most  liverworts,  and  in 
what  respects  ?  Explain  how  this  can  be  in  a  group  (pter- 
idophytes)  higher  than  the  bryophytes.  Under  what  con- 
ditions are  the  eggs  fertilized  ?  What  are  the  life  habits 
at  this  time  ?  What  are  the  chief  advances  of  the  sporo- 
phytes of  ferns  over  those  of  bryophytes  ?  Describe  the 
life  history  and  distinguish  between  the  sexual  phase,  game- 
tophyte, and  the  asexual  phase,  sporophyte.  Draw  and 
arrange  a  series  of  diagrams  illustrating  the  chief  stages 
throughout    the  life   history,  using  two  colored  pencils  to 


MARSILIA  139 

designate  the  gametophytic  and  sporophytic  generations 
respectively  (App.  18).  Construct  a  life-history  formula  that 
will  express  this  succession  (App.  18). 

131.  Fronds,  vegetative  leaves,  and  spore  leaves,  or  sporophylls.  Study  the 
fronds  of  such  fenis  as  Onoclea  sensibiUs,  or  O.  struthiojjteris,  or  Osmunda 
ciunamoinea.  Osmunda  regalts  and  0.  Claytoniaua  illustrate  the  points  out- 
lined below  to  a  partial  extent.  Herbarium  material,  —  that  is  the  fronds 
mounted  on  sheets,  —  may  be  used.  Observe  that  there  are  two  forms 
of  fronds  : 

A.  Vegetative  fronds,  which  may  be  called  vegetative  leaves,  or  sim- 
ply leaves. 

B,  Spore-bearing  fronds,  which  are  called  spore  leaves  or  sporojjhylls. 
The  sporophylls  are  devoted  almost  entirely  to  the  work  of  spore 
production.  They  are  not  expanded;  there  is  relatively  little  green 
tissue,  and  they  are  not  well  suited  to  the  work  of  photosynthesis. 
Thus  the  fronds  of  these  ferns  have  become  differentiated  into  two 
sets,  one  devoted  to  the  purposes  of  spore  production  and  the  other  to 
vegetative  activities. 

Examine  a  series  of  leaves  illustrating  the  general  conditions  stated 
above.  Compare  them  and  draw.  Search  for  leaves  with  mixed  char- 
acters, that  is,  in  parts  devoted  to  spore  production,  and  in  other  parts 
strictly  vegetative.  These  are  not  uncommon,  and  their  study  makes 
clearer  the  relationship  between  the  vegetative  leaves  and  the  spore  leaves 
or  sporophylls.  Ophioglossum,  Botrychium,Aneimia,  and  Lygodium  illus- 
trate excellently  the  mixed  characters  noted  above,  but  material  is  less 
likely  to  be  available.  Some  of  the  common  ferns  —  as  the  Christmas 
fern  {Polystichum  acrostichoides)  —  also  show  the  same  tendencies. 

132.  Marsilia,  a  water  fern.*  Study  the  life  habits  of  the  plant 
as  it  grows  in  the  water  or  in  wet  situations. 

A.    General  morphology.    Note  : 

1.  The  creeping  stem,  or  rootstock  (rhizome). 

2.  The  four-parted  leaves.    Contrast  their  veining  with  that 
of  the  clover  leaf. 

3.  The  fibrous  roots. 

*  To  THE  Instructor  :  If  only  one  heterosporous  pteridophyte  can  be  studied 
in  the  laboratory,  it  is  perhaps  better  that  the  form  be  Selaginclla.  But  the  ease 
with  which  the  spores  of  Marsilia  (especially  M.  vestita)  may  be  pjerniinated  and 
the  gametophytes  obtained,  together  with  the  excellent  study  of  .sperms  and  the 
young  sporophyte,  which  is  offered,  make  it  an  especially  attractive  type  lor 
study,  and  it  should  be  included  in  a  general  course  whenever  possible. 


140  TYPE  STUDIES 

4.  The  spore  fruits  (sporocarps)  borne  in  groups  on  short 
stalks,  attached  to  the  base  of  the  leaf.  The  spore  fruits 
are  modified  portions  of  leaves,  which  are  consequently 
highly  specialized  sporophylls. 

Illustrate  these  features  of  the  general  morphology  in  a 
habit  sketch. 

B.  The  spore  fruit,  or  sporocarp.  Spore  fruits  of  Marsilia  ves- 
tita  open  more  readily  in  water  and  are  generally  more 
favorable  for  this  study  than  those  of  M.  quadrifolia.  Chip 
the  edge  of  a  spore  fruit  with  the  point  of  a  heavy  knife 
and  place  in  water.  It  will  probably  open  in  an  hour  or 
more,  splitting  along  one  side  like  a  pod.    Note : 

1.  The  emergence  of  a  worm-like  gelatinous  structure  bear- 
ing elliptical  spore  masses,  which  are  really  groups  of 
sporangia  and  consequently  sorl.  Make  a  drawing  to  show 
their  appearance  after  emerging  from  the  spore  case. 
Split  a  dry  spore  fruit  lengthwise  and  observe  the  manner 
in  which  the  sori  are  arranged  within.    Illustrate. 

2.  Examine  a  sorus  under  l.p.  Note  the  two  sizes  of  spores, 
the  larger  called  megaspo7'es  and  the  smaller  microspores. 
Show  their  arrangement  in  the  sorus. 

3.  If  the  spore  fruit  has  not  been  in  the  water  too  long,  the 
microspores  will  be  found  in  groups  of  sixty -four,  held 
within  a  very  delicate  tissue  which  represents  a  microspo- 
rangium.  In  this  connection  it  is  important  to  remember 
that  the  common  ferns  produce  sixty-four  spores  in  their 
sporangia. 

C.  The  microspores  and  tnegaspores. 

1.  Draw  the  two  forms  of  spores  side  by  side  to  show  com- 
parative size.  Note  the  slight  protuberance  at  one  end  of 
the  megaspore. 

2.  Crush  the  megaspore  and  stain  the  contents  with  iodine. 
What  are  the  large  grains  ? 

The  spores  begin  to  germinate  at  once,  and  after  eighteen  or 
twenty  hours  develop  small  gametophytes  of  two  forms  :  (1)  male 


MARSILIA 


141 


gametophijtes,  developed  by  the  microspores;  and  (2)  female 
gametophytes,  developed  by  the  megaspores.  The  differentiation 
of  spores  into  two  sizes,  microspores  and  megaspores,  which 
develop  respectively  male  and  female  gametophytes,  is  called 
heterospory. 

D.  The  male  gametophyte.  This  small  structure  can  best  be 
studied  by  means  of  microtome  sections  (see  Principhs, 
Fig.  282,  A).  Living  material  will,  however,  show  the  rup- 
tured microspore,  a  protruding  cellular  papilla,  and,  at  the 
proper  stage,  developing  sj^erms  within.  Draw  such  germi- 
nating spores. 

1.  Sjjerms  are  generally  to  be  found  swimming  about  in  the 
water,  especially  in  the  vicinity  of  megaspores,  which  by 
this  time  have  developed  archegonia,  formed  singly  at  one 
end  of  the  spore.  Excretions  from  the  archegonium  exert 
an  attractive  influence,  called  chemotaxis,  upon  the  sperms. 

2.  Stain  the  sperms  with  iodine.  Note  the  spiral  body,  like 
a  long  corkscrew,  and  the  numerous  cilia  distributed 
over  it.  A  vesicle,  frequently  to  be  found  at  the  larger 
end  of  the  spiral,  is  the  remains  of  the  sperm  mother  cell. 
Draw  the  stained  sperms. 

E.  The  female  gametophyte.  This  consists  of  a  short-necked 
archegonium  developed  at  the  end  of  the  megaspore,  which 
was  marked  by  the  slight  protuberance.  Microtome  sections 
are  necessary  to  show  its  detailed  structure  (see  Frinciples, 
Fig.  282,  C).  In  the  living  material  note  and  show  in  a  figure  : 

1.  The  opening  into  the  short  neck. 

2.  The  arrangement  of  sZme  around  the  archegonium  end 
of  the  megaspore  in  which  sperms  are  frequently  caught. 

3.  The  swollen  base  of  the  archegonium  containing  the  egg. 

Note  the  relatively  small  amount  of  chlorophyll  in  the 
cells  of  the  female  gametophyte.  Where  does  it  get  the 
food  necessary  for  its  development  ? 

F.  The  young  sjyorophyte.  The  sporophyte  begins  to  develop 
at  once  from  the  fertilized  egg.    The  early  stages  of  its 


142  TYPE  STUDIES 

division  differentiate  four  regions,  which  develop  respectively 
into  stem,  root,  first  leaf,  and  a  large  foot.  These  stages  can 
only  be  studied  from  microtome  sections.  The  first  leaf 
and  root  grow  rapidly  and  in  a  few  days  break  through  the 
much-enlarged  archegonium  (calyptra). 

1.  Watch  the  development  of  the  sporophytes  in  a  culture 
of  spores.  When  about  one  week  old  draw  a  megaspore 
with  the  attached  sporophyte  imder  l.p.  Determine  by  the 
root  cap  which  portion  is  root  and  which  leaf.  The  stem 
lies  at  the  base  of  the  leaf.    Where  is  the  foot  ? 

2.  Crush  the  megaspore  and  observe  the  condition  of  its 
food  contents.  What  has  furnished  the  food  for  the 
development  of  the  sporophyte  ? 

Reference.    Campbell,  23. 

Questions.  What  are  the  growth  habits  of  MarsUia  ?  What 
are  the  life  conditions  governing  the  germination  of  the 
spores  and  development  of  the  gametophytes  ?  What  is 
heterospory  ?  What  are  the  advantages  in  the  differentia- 
tion of  a  large  megaspore  richly  supplied  with  food  ?  What 
are  its  advantages  in  giving  the  sporophyte  a  better  start 
in  life  ?  Describe  the  life  history,  distinguishing  between 
the  sexual  phases,  male  and  female  gametophytes,  and  the 
asexual  phase,  sporophyte.  Draw  and  arrange  a  series  of 
diagrams  illustrating  the  chief  stages  throughout  the  life 
history,  using  two  colored  pencils  to  designate  the  gameto- 
phyte  and  sporophyte  generations  respectively  (App.  18). 
Construct  a  life-history  formula  that  will  express  this 
succession  (App.  18). 

THE  HORSETAILS,  OR  EQUISETINE^ 

133.  Equisetum  arvense,  the  field  horsetail.  This  is  the  com- 
monest of  the  horsetails  and  is  abundant  along  railroad  tracks, 
roadsides,  river  banks,  and  bare  northerly  slopes.  The  sjjore- 
bearing  shoots  appear  early  in  April  and  are  followed  shortly  by 


EQUISETUM  143 

the  vegetative  shoots.     Study  the  plant  in  the  field  and  dig  up  the 
underground  rootstocks  (rhizomes).     Note  their  extent  and  the 
manner  in  which  the  plant  establishes  itself  in  the  soil,  its  lux- 
uriance in  waste  ground,  and  its  endurance  of  drought.    It  is  in 
structure  an  excellent  illustration  of  a  xerojjJiyte  (see  FrlncqdeSj 
p.  459),  showing  very  striking  adaptations  to  its  life  habits. 
A.    General   morpliology.    Study  entire    plants,   including  the 
rootstocks.    Well-mounted  herbarium  sheets  of  plants  col- 
lected when  the  spores  are  shed,  and  another  set  collected 
about  a  month  later  are  excellent  for  comparative  study. 
In  plants  collected  in  April  with  spore-bearing  or  fertile 
shoots  note  : 

1.  The  upright,  pale  yellowish,  unbranched  shoots  bear- 
ing cones  at  the  tip  composed  of  six-sided  scales.  These 
shoots  are  the  spore-bearing,  or  fertile  shoots.  Examine 
their  yoiW^o?  structure,  and  in  preserved  material  pull  the 
joints  apart. 

2.  Note  the  toothed  sheaths  at  the  joints  (nodes).  Each 
tooth  repxesents  a  leaf. 

3.  Observe  the  developing,  branched,  vegetative  shoots.  Have 
they  the  same  jointed  structure  with  toothed  sheaths  as 
the  spore-bearing  shoots  ? 

4.  Trace  the  spore-bearing  shoots  and  also  the  develop- 
ing vegetative  shoots  to  the  creeping  rootstock  (rhizome). 
What  is  the  structure  of  the  rootstock  ?  Has  it  joints  ? 
sheaths  ?  Where  do  the  roots  arise  ?  Note  the  tuberous 
bodies,  if  present. 

Illustrate  the  above  features  in  a  habit  sketch,  with  such 
details   of   the  joints  and    sheaths   as    are   necessary  to 
make  clear  the  fundamental  morphology. 
In  plants  collected  somewhat  later,  with  well-developed  vege- 
tative shoots,  note : 

5.  That  the  spore-bearing  shoots  have  died. 

6.  That  the  vegetative  shoots  have  developed  into  tall  green, 
much-branched  stalks.    How  do  they  feel  to  the  touch  ? 


144  TYPE  STUDIES 

7.  Study  the  jointed  structure  of  the  branches,  the  sheaths, 
the  method  of  branching.  AVhat  part  of  the  plant  per- 
forms the  work  of  photosynthesis  ? 

Draw  a  portion  of  the  vegetative  shoot  to  ilhistrate  the 
above  points. 

B.  The  cone  and  its  scales,  or  sporophylls.    Study  from  pre- 
served material. 

1.  Draw  a  cone  in  detail  (if  not  drawn  under  A),  showing 
the  arrangement  of  the  hexagonal  scales  in  circles  around 
the  stem.  Why  should  their  form  be  six-sided  ?  Com- 
pare the  circles  of  scales  with  the  nodes  or  joints  of  the 
stem  bearing  circles  of  leaves  forming  sheaths. 

2.  Cut  off  several  scales,  noting  the  central  stalk  bearing  the 
six-sided  plate  and  the  sac-like  sporangia  hanging  down 
from  the  plate.  Draw  two  side  views  of  the  scales  as 
seen  somewhat  obliquely  from  above  and  below.  The 
scales  are  highly  specialized  spore  leaves,  or  sporophylls. 
What  are  some  of  the  reasons  why  they  should  be  so 
considered  ? 

C.  The  sporangiuni  and  its  spores.    Split  a  sporangium  open 
with  the  point  of  a  needle.     Examine  under  h.p.     Note  : 

1.  The  spores,  each  bearing  four  filamentous  elaters,  devel- 
oped from  four  segments  of  the  outer  spore  wall,  which 
separate  from  one  another  and  the  spore  except  at  one 
point. 

2.  Allow  the  spores  to  become  dry  and  note  the  position  of 
the  elaters.    Draw. 

3.  Breathe  gently  on  the  dry  spores  or  moisten  them  and 
observe  the  behavior  of  the  elaters.    Draw  various  spores. 

\.  Study  the  structure  of  the  sporangium  wall,  the  cells  of 
which  are  irregularly  thickened.  Draw  a  portion  under 
h.p.  How  does  the  sporangium  wall  rupture  ?  What 
mechanical  forces  are  at  work  to  make  it  split  open  ? 

D.  The  cell  structure  or  histologi/   of  the  stem.    Cut   sections 
across  the  stem  between  the  nodes.    Observe  under  l.p.  the 


LYCOPODIUM  145 

air  sjmces,  the  distribution  of  gree7i  tissue,  the  rigid  tissue 

around  the  outside,  the  small  fibro-vascular  handles.    kSIiow 

these  structures  in  an  outline  sketch. 

1.  The  detailed  structure  of  the  stem  is  complicated  and  highly 
specialized  for  its  work  of  photosynthesis  under  severe  xerophytic 
conditions.  There  are  many  interesting  adaptations  to  these  eco- 
logical relations,  as  shown  by  the  position  of  the  stomata  protected 
within  the  lengthwise  grooves,  the  heavy  layers  of  thick-walled  tis- 
sue outside  of  the  green  tissue,  etc.  The  study  of  these  adaptations 
is  veiy  interesting,  but  rather  special,  requiring  well-cut  sections. 

E.  The  growing  points  of  stems  and  roots.  These  are  occupied  by  remark- 
able, large  apical  cells  whose  structure  and  activities  are  best  studied 
by  means  of  microtome  sections.  They  are  among  the  best  illustrations 
of  growth  from  apical  cells. 

F.  The  gametophytes.  These  can  be  obtained  only  by  sowing  spores  when 
very  fresh.  The  prothallia  are  irregularly  lobed  and  the  antheridia 
and  archegonia  are  generally  developed  on  separate  plants  (see  Prin- 
ciples, Fig.  285). 

References.    Campbell,  23;  Goebel,  16. 

Questions.  What  are  the  structural  characters  of  the  horse- 
tails especially  adaptive  to  severe  conditions  of  heat  and 
drought  (xerophytic  conditions)  ?  Where  is  the  work  of 
photosynthesis  performed  ?  Have  the  leaves  anything  to 
do  with  it  ?  Have  the  leaves  any  very  obvious  functions  ? 
Why  are  they  present  especially  on  the  underground  root- 
stock  ?  What  is  the  form  and  structure  (morphology)  of 
the  cone  ?  What  are  some  of  the  advantages  of  the  elaters 
on  the  spores  ?  What  are  the  advantages  in  the  spores 
clinging  together  so  that  they  germinate  in  groups  ? 


THE  CLUB  MOSSES,  OR  LYCOPODINE^ 

134.  Lycopodium,  the  lycopod,  or  club  moss.  Species  of  Lycopodium  with 
well-differentiated  cones,  such  as  L.  annotinum,  L.  complanatuin,  L.  clava- 
tum,  etc.,  furnish  the  best  material  for  type  studies.  Observe  when  possible 
the  life  habits,  noting  the  creeping  stems  from  which  arise  the  upright 
branches  bearinji  cones. 


146  TYPE  STUDIES      • 

A.  General  morphology.  Well-mounted  herbarium  sheets  are  excellent 
for  this  study.    Note  : 

1.  The  upright  stems,  with  spirally  arranged,  needle-shaped  leaves. 

2.  The  long  terminal  cones,  composed  of  spirally  arranged  scales 
(sporophylls). 

3.  The  creeping  stems  with  leaves  similar  to  those  of  the  upright  stems, 

4.  The  rather  infrequent  roots. 

Illustrate  the  above  features  in  a  habit  sketch. 

B.  The  cone  and  its  scales,  or  sporophylls.    Examine  preserved  material. 

1.  Draw  a  cone  in  detail,  showing  the  spiral  arrangement  of  its  scales 
(sporophylls)  if  not  illustrated  under  A. 

2.  Cut  off  several  scales  and  draw  one  as  seen  from  the  inside,  showing 
the  large  sporangium  at  its  base. 

3.  Construct  a  diagram  illustrating  the  attachment  of  the  scales  to  the 
axis  of  the  cone  and  the  way  in  which  they  overlap  one  another. 

The  scales  arCspecialized  spore  leaves,  or  sporophylls.    What  are  some  of 
the  reasons  why  they  should  be  so  considered  ? 

C.  The  sporangium  and  its  spores.  Split  a  sporangium  open  and  note  the 
immense  number  of  minute  spores.  Draw  a  group.  What  is  the  sig- 
nificance of  the  angles  along  one  side  ?  Like  the  spores  of  the  bryo- 
phytes  and  pteridophytes  generally,  they  are  developed  in  groups  of 
four,  tetrads,  from  spore  mother  cells. 

D.  The  cell  structure,  or  histology  of  the  stem  and  leaf.  This  is  a  profitable 
but  detailed  study. 

1.  Cut  cross  sections  of  the  stem.  Note  the  epidermis,  the  thick  corti- 
cal regions  of  ground  tissue,  the  vascular  strands  called  leaf  traces, 
leading  out  to  the  leaves  from  the  central  flbro-vascular  bundle.  In 
the  fibro-vascular  bundle  observe  the  more  or  less  parallel  regions  of 
wood  (xylem),  composed  of  large  tracheids,  and  hast  (phloem)  within 
the  bundle  sheath.  Draw  the  details  of  cell  structure  in  a  series  of 
figures  from  cross  and  lengthwise  sections. 

2.  Examine  the  surface  of  the  leaves  for  stomata.  Cross  sections  of 
the  leaves  will  show  their  simple  cell  structure. 

E.  The  germination  of  spores,  and  the  gametophytes.  Gametophytes  have 
not  been  found  in  America  and  the  spores  have  not  been  germinated 
beyond  the  first  few  cell  divisions.  The  propagation  of  plants  is 
chiefly  by  the  branching  of  stems  which  separate  as  older  parts  die 
away,  and  in  some  species  by  peculiar  vegetative  buds. 

Reference.     Campbell,  28. 

135.  Selaginella.   Various  species  of  Selaginella  have  quite  differ- 
ent habits  of  growth  and  arrangements  of  leaves  and  branches. 


sp:laginklla  147 

S.  riqjestris  is  generally  the  most  available  of  our  native  species, 
but  >S^.  02nis  is  often  easily  obtained.  S.  Kraussiana  is  a  delicate 
form  frequently  cultivated  in  conservatories.  S.  Martensii  and 
other  tropical  species  are  large,  erect,  much-branched,  ornamental 
plants  cultivated  in  greenhouses,  and  when  in  good  fruit  are  ex- 
cellent for  type  study.  A  single  plant  in  fruit  will  supply  a  large 
class  with  material,  but  the  smaller  species  are  also  good. 
A.    General  morphology.    Note  : 

1.  The  character  of  the  sterns^  upright  or  creeping.  Describe 
their  method  of  branching,  generally  in  one  plane. 

2.  The  scale-like  leaves.  These  are  spirally  arranged  in  some 
species  (as  S.  rupestris),  but  in  other  forms  are  distributed 
in  four  rows  and  are  of  two  sizes.  What  is  their  arrange- 
ment in  the  type  studied  ?  Have  the  stems  an  upper  and 
lower  side  (dorsiventral  symmetry)  ?  What  advantage  is 
there  in  this  symmetry  in  relation  to  the  spreading  habits 
of  growth  ?  Search  for  a  very  small  triangular  structure, 
called  the  ligule,  at  the  base  of  the  leaf.  Its  significance 
is  not  known. 

3.  The  spike-like  cones  composed  of  crowded  scales  (sj^oro- 
phylls).  How  are  these  arranged  ?  How  many  rows  ? 
What  is  the  geometrical  form  of  the  cone  ? 

4.  The  fibrous  forking  roots.  In  tropical  species  roots  may 
be  developed  from  the  tips  of  special  descending  branches 
(rhizophores). 

Illustrate  the  above  points  in  habit  sketches,  paying  special 
attention  to  the  arrangement  of  the  leaves  on  the  stem. 
B.   The  cone  and  its  scales,  or  sporophylls. 

1.  Draw  a  cone  in  detail,  showing  the  arrangement  of  the 
scales,  or  sporophylls  (if  not  illustrated  under  A). 

2.  Note  the  sporangium  attached  at  the  base  of  each  sporo- 
phyll.  Are  the  upper  and  lower  sporangia  of  the  same 
cone  alike  ?  Cut  off  the  scales  and  compare  them,  dis- 
tinguishing between  oval  sporangia  containing  minute 
spores,  microspores,  and  larger-lobed  sporangia  containing 


148  TYPE   STUDIES 

a  few  very  large  spores,  megaspores.    These  two  forms  of 
sporangia  are  termed  respectively  microsporangia  and  mega- 
sporangia,  and  the  scales  which  bear  them  are  m/icrosporo- 
phylls  and  viegasporophylls.    Draw  the  microsporophylls 
and  megasporophylls,  viewed  from  the  inside,  showing  the 
form  of  the  sporangia. 
3.  Construct  a  diagram  illustrating  the  attachment  of  the 
two  forms  of  scales  to  the   axis  of  the  cone  and  their 
distribution  above  and  below. 
The  scales,  as  stated  above,  are  sporopliylls  differentiated  into 
two  forms.    What  are  the  reasons  why  they  should  be  so  consid- 
ered ?    The  differentiation  of  spores  into  two  sizes,  microspores 
and  megaspores,  which  develop  respectively  male  and  female 
gametophytes,  is  called  heterospory. 

C.  The  'tmcrosporangiuvi  and  microspores.  Split  a  microspo- 
rangium  open  and  note  the  immense  number  of  minute 
microspores.  Draw,  under  h.p.,  a  portion  of  the  wall  of 
the  sporangium,  showing  the  cell  structure,  and  a  group  of 
spores. 

D.  The  megasporajiglum  and  imegaspores.  Split  a  megasporan- 
gium  open  and  count  the  large  megaspores.  Is  the  number 
the  same  in  all  sporangia?  Draw  a  megaspore  under  h.p., 
showing  the  form  and  markings  on  the  wall.  What  is  the 
significance  of  the  angles  on  one  side  ?  Like  the  spores 
of  the  bryophytes  and  pteridophytes  generally,  and  also 
like  the  microspores,  they  are  developed  in  groups  of  four, 
tetrads,  from  spore  mother  cells.  Under  the  same  magnifica- 
tion draw  a  microspore  by  the  side  of  the  megaspore  to 
show  comparative  size. 

E.  The  cell  structure^  or  histology  of  stems  and  leaves. 

1.  Cut  cross  sections  of  the  stem.  Note  the  epidermis  and  the  cortical 
ground  tissue  surrounding  two  or  more  air  spaces  crossed  by  delicate 
filaments.  In  the  center  of  each  space  lies  Sijibro-vascular  bundle 
consisting  of  a  strand  of  wood  (xylem)  surrounded  by  bast  (phloem). 
The  further  examination  of  these  elements  in  cross  and  lengthwise 
sections  may  constitute  a  detailed  study. 


SELAGINELLA  149 

2.  Coraparp  tlio  cell  stnicture  of  very  young  leaves  with  that  of  older 
ones.  The  cells,  in  the  younger  leaves,  contain  a  single  large  chro- 
raatophore,  which  becomes  divided  into  a  cliain  of  segments  in  the 
older  cells. 

F.  The  germination  of  spores,  and  the  gametophytes.  The  microspore  pro- 
duces a  very  small  male  gametophyte,  which  remains  contained  within 
the  ruptured  spore  wall  and  develops  two-ciliate  sperms  (see  Prin- 
ciples, Fig.  290,  A,  B).  The  megaspore  gives  rise  to  a  small  female 
yametophyte,  which  emerges  somewhat  from  the  ruptured  spore  and 
develops  several  archegonia  (see  Principles,  Fig,  290,  C).  The  develop- 
ment of  these  gametophytes  requires  several  weeks,  and  their  study 
demands  microtome  sections,  which  are  difficult  to  prepare,  so  that 
they  can  hardly  be  treated  in  an  elementary  course.  Marsilia  (Sec.  132) 
is  a  better  type  for  the  study  of  reduced  male  and  female  gametophytes 
associated  with  microspores  and  megaspores. 

G.  The  development  of  the  sporophyte.  This  study,  like  that  of  gameto- 
phytes, requires  microtome  sections  of  material  difficult  to  obtain  and  to 
cut,  and  is  hardly  practicable  for  a  general  course.  Marsilia  (Sec.  132)  is 
a  better  type  to  illustrate  the  relation  of  the  embryo  sporophyte  to  the 
female  gametophyte  in  heterosporous  pteridophytes.  The  embi-yo  de- 
velops in  the  interior  of  the  gametophyte  at  the  end  of  a  structure 
called  the  suspensor.  Three  regions  are  differentiated,  — the  stem  with 
young  leaves  forming  a  bud,  the  root,  and  the  large /ooi  (see  Principles, 
Fig.  290,  C).  The  foot  absorbs  food  from  the  tissue  of  the  gameto- 
phyte within  the  megaspore.  In  certain  species  of  Selaginella,  as  S.  ru- 
pestris,  the  sporophytes  are  developed  while  the  megaspores  are  still  held 
mechanically  by  the  sporophylls  on  the  cone  (see  Principles,  Fig.  290, 
D).  This  retention  of  the  megaspores  on  the  sporophyte  is  suggestive 
of  the  seed  habit  (see  Principles,  pp.  335  and  330). 

Reference.    Campbell,  23. 

Questions.  What  are  the  growth  habits  of  the  type  of  SeUiyl- 
nella  which  has  been  studied  ?  Are  there  any  xerophytic 
adaptations  ?  Describe  any  peculiarities  in  the  arrangement 
of  the  leaves  and  suggest  reasons  therefor.  What  is  the 
form  and  structure  (morphology)  of  the  cone  ?  Why  are  its 
leaves  called  sporophylls  ?  What  is  the  relation  between  the 
large  size  of  the  megaspores  and  their  production  relatively 
few  in  a  megasporangium  ?  What  is  heterospory  ?  What 
are  its  advantages  in  giving  the  sporophyte  a  better  start  in 


150  TYPE  STUDIES 

life  ?  Describe  the  life  history,  distinguishing  between  the 
sexual  phases,  gametophytes,  and  the  asexual  phase,  sporo- 
phyte.  Draw  and  arrange  a  series  of  diagrams  illustrating 
the  chief  sta,ges  throughout  the  life  history,  using  two  col- 
ored pencils  to  designate  the  gametophytic  and  sporophytic 
generations  respectively  (App.  18).  Construct  a  life-history 
formula  that  will  express  this  succession  (App.  18). 

136,  Isoetes,  quillwort.    Study  when  possible  the  life  habits,  noting  whether 
the  form  is  aquatic  or  terrestrial. 

A.  General  morphology.    Note  : 

1.  The  rush-like  leaves  arranged  around  a  very  short,  conical  stem,  and 
the  cluster  of  forking  roots  below.  Illustrate  in  a  habit  sketch. 
These  leaves,  late  in  the  season,  produce  sporangia  at  their  bases, 
thus  becoming  sporophylls.  At  such  times  the  stem  may  be  com- 
pared to  a  cone  of  sporophylls. 

2,  Strip  the  sporophylls  from  the  stem.  Those  on  the  outside,  and 
consequently  lower  on  the  stem,  are  likely  to  be  megasporophylls,  as 
shown  by  the  basal  sporangium  containing  megaspores.  Those  in 
the  interior,  and  consequently  higher  up  on  the  stem,  are  likely  to 
be  microsporophylls,  as  shown  by  the  basal  sporangium  containing 
microspores. 

B.  The  sporophylls.  Examine  the  base  of  a  megasporophyll,  viewing  it 
from  the  inner  side.    Show  in  a  figure  : 

1.  The  large  megasporangium  containing  megaspores,  held  in  a  hol- 
low at  the  base  of  the  leaf  and  partially  covered  by  a  membrane, 
the  velum. 

2.  The  ligule,  a  triangular  scale  situated  on  the  sporophyll  above 
the  sporangium.  Diagram  the  position  of  the  ligule  and  sporan- 
gium as  they  appear  in  a  lengthwise  section  of  the  base  of  the 
sporophyll. 

3.  Draw  the  megaspore  under  h,p,,  showing  the  markings  on  the  thick 
wall  and  the  angles  on  one  side.    What  do  the  angles  signify  ? 

4.  Compare  the  base  of  a  microsporophyll  with  that  of  a  megaspo- 
rophyll. 

5.  Draw  a  group  of  microspores  under  h.p.  to  show  their  size  in  com- 
parison with  that  of  the  megaspore. 

C.  The  structure  of  the  leaf.  Section  the  leaf  across  and  lengthwise,  Note 
the  large  air  spaces  separated  by  partitions.  Show  their  arrangement 
in  an  outline  drawing  and  the  small  fibro-vascular  6itndZe  traversing  the 
interior  of  the  leaf.    Are  stomata  present  ? 


THE  PINE  151 

D.  The  gametophytes.  The  germination  of  the  spores  of  Isoetes  and  tlic 
development  of  the  gametophytes  is  even  more  difldcult  to  follow  than 
that  of  Selaginella  and  requires  detailed  study. 

Reference.    Campbell,  23. 


THE  GYMNOSPERMS,  OR  GYMNOSPEKM^ 

137.  Cycads.  Cycas  revoluta  is  a  large  form  frequently  cultivated  in  park 
conservatories,  and  may  be  used  to  illustrate  the  general  morphology  of  the 
cycads,  that  is,  the  trunk-like,  unbranched  stem  bearing  the  crown  of  com- 
pound leaves  at  the  top.  This  cycad  occasionally  develops  sporophylls  in 
the  greenhouses,  which  may  then  be  collected  and  preserved  for  study. 
The  carpels  are  developed  more  commonly  than  the  stamens. 

Zamia  is  a  small  cycad  which  grows  in  Florida  and  is  an  admirable  type 
for  a  study  of  the  cycad  cone,  together  with  the  development  of  the  ovules 
and  pollen,  the  structure  of  the  male  and  female  gametophytes,  processes  of 
fertilization,  and  development  of  the  embryo.  Cones  of  Zamia  may  be  readily 
shipped,  and  since  the  ovules  retain  their  vitality  for  a  considerable  time 
they  can  be  studied  alive  in  the  North  or  killed  and  preserved  for  micro- 
tome sections.  Zamia  may  also  be  readily  grown  from  seed  in  greenhouses, 
and  will  produce  cones  under  cultivation.  Its  study  is  recommended  wher- 
ever possible. 

138.  The  pine  (App.  21)..  Several  species  are  available  for  this 
study,  such  as  the  Scotch  pine  (Finns  sylvestris),  the  Austrian 
pine  (P.  laricio),  F.  Strobus,  F.  palustris,  or  some  of  the  scrub 
pines,  such  as  F.  Banksiana.  Living  material  for  general  mor- 
phological or  histological  work  may  be  obtained  at  any  time  of 
year.  The  young  cones  should  be  collected  and  preserved  in  alco- 
hol at  the  time  of  pollination  in  May,  when  the  year-old  cones 
may  also  be  gathered  and  preserved  for  comparison  with  the 
first.  Dried,  open  cones  and  seeds  should  be  collected  in  the  late 
summer  or  autumn.  The  pine  should  also  be  studied  in  the  field 
to  determine  its  growth  habits  and  the  ecological  adaptations  of 
its  foliage  to  conditions  of  severe  cold  and  drought. 

A.    General  morphology.    Observe  : 

1.  The  main  stem  and  hranchrs^  eacli  ending  in  a  terminal 
hud  ;  the  arrangement  of  the  branches. 


152  I'VPK  STUDIES 

2.  The  very  numerous  divarf  branches,  each  bearing  a  cluster 
(fascicle)  of  two,  three,  or  more  needle-like  hooves,  accord- 
ing to  the  species  studied. 

3.  The  thin  scales  on  the  dwarf  branches  wrapped  around 
the  base  of  the  cluster  of  needle  leaves.  Are  these  scales 
morphologically  leaves  ?    Why  ? 

4.  The  bases  of  old  scales  spirally  arranged,  and  covering 
the  main  branches  from  the  axils  of  which  the  dwarf 
branches  arise.  Younger  full-sized  scales  at  the  tips  of 
the  shoots.    What  are  these  scales  morphologically? 

5.  The  bud  scales,  or  leaves,  enveloping  the  terminal  bud. 
Illustrate   these   features   in   habit   sketches.     How   many 

forms  of  leaves  are  there  on  the  pine? 

6.  On  a  branch  two  feet  or  more  in  length  note  the  regions 
that  indicate  the  beginnings  of  one  year's  growth  and  the 
end  of  another's.  Draw  such  a  region  and  explain  the 
peculiar  arrangement  of  the  scales  upon  it. 

7.  Observe  the  position  of  cones  on  the  branches.  How 
many  sizes  do  you  find  and  what  are  their  ages  as  shown 
by  their  positions  ? 

8.  Note  the  branch  scars  on  older  portions  of  the  stem  and 
main  branches. 

B.  The  cell  structure,  or  histology,  of  the  stem.  Cut  cross  sections  of  a 
three-  or  four-year-old  branch.  These  may  be  stained  witli  advantage 
(Sec.  212)  and  mounted  in  balsam. 

1.  Observe  under  l.p. :  (a)  tlie  restricted  region  of  pith;  (&)  the  layers 
or  rings  of  wood,  or  xylem,  around  the  pith  (what  is  the  significance 
of  their  number  ?) ;  (c)  a  layer  of  bast  or  phloem  outside  of  the  w^ood 
and  separated  from  it  by  a  thin  cambium ;  (d)  the  outer  bark  com- 
posed of  larger  cells,  in  places  green,  but  on  the  exterior  dead 
and  forming  scales  ;  (e)  medullary  rays  appearing  as  radiating  lines 
running  through  the  wood  and  bast ;  (/)  resin  ducts  in  the  wood 
and  outer  bark.  Are  the  medullary  rays  of  the  same  length  ?  Do 
any  of  them  penetrate  to  the  pith  ? 

Show  the  position  of  these  tissues  in  an  outline  sketch. 

2.  Study  the  structure  of  the  wood  in  the  region  between  the  growth 
of  two  successive  years.    In  a  detailed  figure  show  the  form  of  the 


THE    PINE  "153 

empty  wood  cells  and  explain  dii'terences  in  size.  Also  include  in 
the  figure  a  medullary  ray,  the  cells  of  which  have  dense  protoplas- 
mic contents,  and  also  a  resin  duct.  Note  the  cross  sections  of  pits 
in  the  wood  cells,  which  will  be  better  undei:stood  after  the  study 
outlined  in  C.    In  what  faces  of  the  cells  are  they  found  ? 

3.  Study  the  region  of  the  cambium  and  show  the  form  of  its  cells  in 
a  detailed  figure,  together  with  some  of  the  wood  on  the  inside  and 
the  bast  on  the  outside,  including  a  medullary  ray.  The  bast  is 
composed  for  the  most  part  of  sieve  tubes.  What  are  the  peculiari- 
ties of  the  cambium  tissue  characteristic  of  a  region  of  growth  ? 

4.  Study  the  outer  bark,  showing  in  figures  (a)  the  form  of  the  old 
bast  cells  having  a  crushed  appearance  ;  (6)  the  green  parenchyma, 
comparing  it  with  the  pith  ;  (c)  the  manner  in  which  the  medullary 
rays  merge  with  the  cells  of  the  bark. 

.  Cell  structure  of  the  wood.  Use  the  cross  sections  employed  above  and 
also  radial  (lengthwise)  sections  and  tangential  (lengthwise)  sections, 
staining  if  desired  (Sec.  212). 

1.  In  radial  sections  note  (a)  the  long,  empty  wood  cells,  trachelds, 
with  walls  bearing  bordered  pits  (pits  characterized  by  two  circles  and 
peculiar  to  certain  groups  of  gymnosperms) ;  (b)  the  medullaiy  rays, 
like  long  knife  blades,  piercing  the  wood,  mostly  composed  of  cells 
with  dense  protoplasmic  contents  but  some  of  them  empty  and 
pitted.    Show  these  points  in  a  detailed  figure. 

2.  In  tangential  sections  note  (a)  the  wood  cells,  tracheids,  with  cross 
sections  of  the  bordered  pits  ;  (6)  the  cross  sections  of  the  medul- 
lary rays.    Illustrate  in  a  detailed  figure. 

3.  Examine  the  cross  sections  again  to  understand  clearly  the  appear- 
ance of  the  pits  and  medullaiy  rays  in  the  light  of  your  study  of 
radial  and  tangential  sections.  Make  a  new  figure  if  the  study  out- 
lined in  B,  2,  is  not  satisfactory. 

4.  Draw  a  cross  section  of  a  pit,  showing  the  delicate  membrane,  or 
primitive  cell  wall  (middle  lamella),  which  crosses  it,  and  thesecond- 
aiy  thickening  of  the  cell  wall  on  both  sides. 

6.  Construct  a  figure  of  the  appearance  of  a  cube  of  wood  under  high 

magnification,  several  cells  wide,  as  viewed  from  an  angle  so  as  to 

show  cross,  radial,  and  tangential  sections  (App.  21).    InchuU'  in  this 

figure  also  one  or  more  medullary  rays  and  a  resin  duct. 

The  cell  structure,  or  histology,  of  the  pine  needle.    Cut  cross  sections  of 

a  pine  needle  free-hand  (Sec.  194)  or  use  prepared  slides  (Sec.  212). 

Observe : 

1.  The  heavy  epidermis,  with  lengthwise  grooves,  in  which  are  situated 
the  stomata. 


154  TYrE  STUDIES 

2.  The  layer  of  rigid  tissue  (sclerencliyma)  beneath  the  epidermis. 

3.  The  broad  layer  of  green  tissue,  mesophyll,  whose  cells  have  in- 
folded walls. 

4.  Resin  ducts  in  the  green  tissue. 

5.  A  central  area  containing  in  most  species  of  pine  two  fibro-vascular 
bundles  and  bounded  by  a  bundle  sheath.  The  fibro-vascular  bundles 
lie  in  a  special  region  of  so-called  transfusion  tissue,  composed  in 
part  of  empty  pitted  cells  and  in  part  of  cells  containing  protoplasm. 
Each  bundle  consists  of  a  region  of  wood  (xylem)  and  bast  (phloem) 
and  contains  rather  ill-defined  medullary  rays. 

6.  The  sections  of  the  stomata  show  epidermal  cells  on  either  side  of 
the  groove  and  below  them  two  small  guard  cells  containing  chloro- 
phyll.   Each  stoma  opens  into  a  chamber  within  the  green  tissue. 

Show  the  position  of  the  tissues  of  the  needle  in  an  outline  drawing 
and  then  treat  the  details  in  separate  figures. 

E.  The  stmiiinate  cones.  These  are  short-lived  structures  de- 
veloped in  the  late  spring  with  the  appearance  of  the  new 
growth  from  the  terminal  buds.  They  are  variously  clustered 
in  different  species  of  pine.  Draw  a  habit  sketch  of  a  group, 
showing  the  arrangement  of  the  cones  on  the  new  growth, 
with  its  developing  needles. 

1.  Observe  the  position  of  the  staminate  cone  in  the  axil  of 
a  pointed  scale  leaf.  Draw  in  side  view  to  show  the  some- 
what spiral  arrangement  of  the  closely  crowded  stamens 
(microsporophylls). 

2.  Split  the  cone  lengthwise  and  diagram  the  attachment  of 
the  stamens  along  its  axis.  What  is  the  morphology  of 
the  staminate  cone  as  indicated  by  its  position  on  the  stem 
and  the  nature  of  the  stamens  (see  F  below)  ? 

F.  The  stamen  and  pollen.  Remove  a  stamen  from  a  cone 
which  has  not  yet  shed  its  pollen. 

1.  Observe  its  form  and  structure,  —  a  short  stalk,  broaden- 
ing beyond,  on  the  lower  face  of  which  are  borne  long  pollen 
sacs  (microsporangia).  The  tip  of  the  stamen  is  turned 
upwards  and  fits  over  the  pollen  sacs  of  the  stamen  above. 
Draw  under  a  hand  lens  the  stamen  in  end  and  side  views 
to  illustrate  these  points. 


THE   PINE  156 

2.  Open  a  pollen  sac  and  mount  the  pnllen  yrains  (micro- 
spores) in  water.    Under  h.p.  note  (a)  the  two  ivlngs  at- 
tached to  the  pollen  grain  ;  these  arc  developed  from  the 
outer  wall  of  the  cell ;   (b)  within  the  pollen  grain  the  tube 
7iucleus  lying  near  the  center  and  the  generative  cell  against 
the  wall  at  the  side  farthest  away  from  the  wings,  also 
occasional  remains  of  a  lyrothalllal  cell  between  the  gener- 
ative cell  and  the  wall.    Draw  a  pollen  grain  showing  this 
structure. 
The  pollen  grains  are  developed  in  groups  of  four,  tetrads, 
within  polleyi  mother  cells.    Their  method  of   formation  shows 
them  to  be  microspores,  and   the  pollen   sac  is  consequently  a 
m'icrosporangium  and  the  stamen  a  mlcrosporopJujll.    The  nuclear 
and  cell  divisions  within  the  pollen  grain  are  stages  in  the  germi- 
nation of  this  microspore  to  form  the  male  gametophijte. 

G.  TJie  carpjellate  cone  at  the  time  of  pollination  and  its  scales. 
These  cones  appear  on  the  new  growth  from  the  terminal 
buds  in  the  late  spring  at  the  same  time  as  the  staminate 
cones.  They  are  borne  singly  or  in  groups  of  two  or  three  at 
the  tips  of  branches.  Draw  a  habit  sketch  of  the  carpellate 
cones  on  the  new  growth. 

1.  Draw  a  side  view  of  the  carpellate  cone,  showing  the 
spiral  arrangement  of  the  co7ie  scales.  Each  scale  is  be- 
lieved to  be  a  group  of  fused  carpels  or  megasporophylls. 

2.  Detach  a  cone  scale  carefully  and  draw  it  viewed  from  the 
inner  face.  Note  (a)  the  two  ovules  at  either  side  of  its 
base,  each  with  two  horn-like  aj^pendages  ;  (b)  a  poitit  on 
the  cone  scale  above  the  ovules  and  between  them. 

3.  Draw  a  side  view  of  the  cone  scale,  noting  a  small  bract 
in  the  axil  of  which  the  cone  scale  is  borne. 

The  ovule  is  a  megasjjorangium  with  a  protective  envelope,  the 
integument,  but  the  evidence  for  this  conclusion  can  only  be 
understood  after  the  study  of  sections  of  later  stages  (see  J). 

H.  The  year-old  carpellate  cone  and  its  scales.  Search  for  year- 
old  cones,  establishing  their  identity  by  their  position  on 


156  TYPE   STUDIES 

the  branches.  Compare  their  size  and  texture  with  the  car- 
pellate  cones  at  the  time  of  pollination.  Draw  a  side  view  of 
the  cone,  if  time  permits,  and  then  detach  a  scale  and  draw 
two  views  as  described  in  G,  2,  3,  noting  and  comparing  the 
relative  position  of  the  structures  described  there. 
I.  The  mature  carpellote  cone  and  its  scales.  Study  mature 
cones  collected  in  the  late  summer  or  autumn.  Compare 
their  size  and  texture  with  the  year-old  cones  and  the  cones 
at  the  time  of  pollination. 

1.  Draw  a  side  view,  if  time  permits. 

2.  Cut  into  the  cone  with  a  heavy  knife,  carefully  detaching 
one  of  the  scales.  Draw  the  scale  as  viewed  from  the  inner 
face,  noting  (a)  that  the  ovules  are  ripening  into  winged 
seeds,  the  wings  developing  from  a  tissue  that  separates 
from  the  inner  face  of  the  scale ;  (b)  the  relative  position 
of  the  point,  above  and  between  the  maturing  seeds. 

3.  Draw  a  side  view  of  the  cone  scale  to  show  the  position 
of  the  bract  in  the  axil  of  which  the  cone  scale  is  borne 
and  the  relation  of  parts  in  comparison  with  the  cone  scale 
at  the  time  of  pollination. 

J.  The  ovule  on  the  year-old  cone.  Sections  of  the  ovule  on 
the  scales  from  a  year-old  cone  may  be  cut  free-hand,  but 
stained  microtome  sections  are  much  more  satisfactory  (Sec. 
212).  They  should  be  cut  lengthwise  of  the  ovule  and  per- 
pendicular to  the  surface  of  the  scale.    Observe  : 

1.  The  enveloping  integument  meeting  at  the  tip  of  the  ovule 
where  there  was  formerly  an  opening,  the  micropyle,  at 
the  time  of  pollination. 

2.  Within  the  integument  and  below  the  micropyle  the 
pollen  chamber  in  which  germinated  pollen  grains  may  be 
found  sending  their  tidies  into  the  interior  of  the  ovule. 

3.  A  conical  structure,  the  nucellus,  into  which  the  pollen 
tubes  have  grown,  lying  within  the  integument. 

4.  A  large  area  in  the  interior  of  the  nucellus,  called  the 
embryo  sac,  which  contains  a  delicate  tissue,  endosperm, 


THE  PINE  157 

and  at   the  micropylar  end  several    reduced    archegonia 
with  very  large  eggs. 
Show  in  an.  outline  drawing  the  relations  of  the  structures 
described  above,  treating  such  details  as  are  possible  in 
separate  figures. 
The  endosperm,  with  the  archegonia  and  eggs,  constitutes  the 
female  gametophyte,  derived  from  a  megasjjore  which  became  the 
embryo  sac.    The  megaspore  was  one  of  a  group  of  four  cells, 
tetrad,  formed  in  the  interior  of  the  nucellus,  which  is  conse- 
quently a  megasporangium.     The  integument  is  a  special  protec- 
tive envelope,  possibly  comparable  to  an  indusium.    The  pollen 
tubes  are  later  developments  of  the  male  gametophytes  formed 
by  the  germination  of  the  microspores  or  pollen  grains. 

The  morphology  of  the  cone  scale  has  been  and  is  still  a  diffi- 
cult problem.  Because  of  the  arrangement  of  the  fibro-vascular 
bundles  in  the  scale  there  are  reasons  for  believing  it  to  be  a 
group  of  fused  megasporophylls  or  carpels,  probably  two  fertile 
carpels,  each  bearing  an  ovule,  and  possibly  a  third  sterile  carpel 
represented  by  the  point  on  the  scale,  situated  above  and  between 
the  ovules.  The  cone  scale  is  therefore  much  more  complex  than 
the  stamen.  According  to  this  theory  the  cone  scale  is  a  group 
of  megasporophylls  in  the  axil  of  a  bract,  and  the  carpellate  cone 
is  not  a  simple  cluster  of  sporophylls  arranged  along  a  shoot 
(like  the  staminate  cone),  but  is  a  compound  structure  consisting 
of  groups  of  sporophylls  in  the  axils  of  bracts.  The  staminate 
cone  has  the  same  morphology  as  the  cones  of  club  mosses  and 
some  simple  flowers  of  angiosperms,  but  the  carpellate  cone  is 
comparable  to  an  inflorescence,  or  cluster  of  flowers,  each  cone 
scale  representing  a  highly  modified  flower. 

K.  The  gametophytes.  A  full  study  of  the  gametophytes  of  the  pine 
would  require  the  examination  of  stages  in  material  covering  many 
months  of  development,  which  is  impracticable  in  a  general  course. 
In  slides  of  the  stage  treated  in  J  it  will  be  possible  to  determine 
the  following  structures  : 

1.  In  the  female  gametophyte  :  (a)  the  delicate  cell  structure  of  the 
endosperm ;  (6)  the  protoplasmic  structure  of  the  large  egg  with  its 


158  TYPE  STUDIES 

prominent  nucleus ;  (c)  frequently  the  presence  of  a  single  canal 
cell  (ventral  canal  cell)  above  the  egg  ;  {d)  a  layer  of  cells  differen- 
tiated from  the  endosperm,  forming  a  jacket  around  the  egg ;  (e)  one 
or  two  tiers  of  cells,  four  cells  in  a  tier,  above  the  egg,  and  repre- 
senting the  neck  of  the  much-reduced  archegonium  (see  Principles, 
Fig.  300,  D). 
2,  In  the  male  gametophyte :  should  the  tips  of  pollen  tubes  be  found 
entering  the  necks  of  archegonia  they  may  be  expected  to  show  two 
large  sperm  nuclei,  and  possibly  the  remains  of  the  tube  nucleus,  now 
degenerating,  with  that  of  the  stalk  cell  also. 

L.  The  seed.  Take  seeds  from  an  open  cone.  It  generally  opens 
at  the  end  of  the  second  summer,  when  the  cone  is  approxi- 
mately one  year  and  four  months  old.  Sketch  to  show  the 
wings.  Section  such  seeds,  or,  better  still,  cut  open  some  of 
the  large  edible  seeds  of  the  nut  pines,  piiion,  obtainable 
from  fruit  dealers.    Note  : 

1.  The  tough  seed  coat,  or  testa,  which  is  the  ripened  integu- 
ment, and  beneath  the  testa  a  membranous  seed  coat  which 
is  largely  the  remains  of  the  nucellus. 

2.  The  endosperm,  filling  the  seed  except  for  the  embryo. 
The  former  is  a  development  from  the  endosperm  of  the 
embryo  sac  and  consequently  gametophytic  in  character. 

3.  The  straight  embryo,  developed  from  a  fertilized  egg, 
attached  to  the  micropylar  end  of  the  seed  by  a  suspensor 
and  imbedded  in  the  endosperm.  The  embryo  consists  of 
a  short  hypocotyl,  bearing  above  a  circle  of  cotyledons. 

Construct  a  diagram  of  a  lengthwise  section  of  a  seed  to 
show  these  structures  in  relation  to  one  another. 
M.  The  germination  of  the  seed.  The  pine  seed  germinates 
rather  slowly,  but  it  will  be  of  interest  to  plant  some  and 
watch  them  as  they  sprout,  comparing  them  with  such  seed- 
lings of  the  angiosperms  (squash,  bean,  pea,  corn,  etc.)  as 
may  have  been  studied. 

Reference.    Principles,  Sees.  350-356. 

Questions.  What  are  the  growth  habits  of  the  pine  ?  What 
are  the  peculiarities  of  its  foliage  ?  its  adaptation  to  drought 


JUNIPER  AND  ARHOR  YITA:  1;VJ 

and  cold  ?  AVhere  is  the  resin  and  turpentine  formed  ? 
Can  you  suggest  any  advantage  to  the  plant  in  its  produc- 
tion ?  How  and  when  is  pollen  formed  and  how  abmidaiitly  ? 
How  does  it  reach  the  ovule ''  What  is  the  history  of  tlie 
carpellate  cone  after  pollination  ?  When  are  the  seeds 
ripened  ?  What  is  the  morphology  of  the  pollen  grain  ? 
Describe  the  male  gametophyte,  with  its  habits,  after  the 
germination  of  the  pollen  grain  in  the  pollen  chamlj(.'r. 
Describe  the  structure  of  the  ovule.  Describe  the  female 
gametophyte  and  its  life  habits  within  the  nucellus  (mega- 
sporangium).  From  what  does  the  embryo  arise  and  how 
does  it  obtain  the  food  for  its  development?  How  many 
generations  are  represented  in  the  tissues  of  the  seed  ? 
Describe  the  life  history,  distinguishing  between  the  sexual 
phases,  gametophytes,  and  the  asexual  phase,  sporophyte. 
Draw  and  arrange  a  series  of  diagrams  illustrating  the  chief 
stages  throughout  the  life  history,  using  two  colored  pencils 
to  designate  the  gametophytic  and  sporophytie  generations 
respectively  (App.  18).  Construct  a  life-history  formula  that 
will  express  this  succession  (App.  18). 

139.  The  morphology  of  the  juniper  and  arbor  vitae.  The  juniper  {Junipcrus) 
and  arbor  vitce  (Thuya)  are  interesting  types  to  study  comparatively  with 
the  pine  :  (1)  as  regards  the  arrangement  and  forms  of  the  leaves  and  conse- 
quent appearance  of  the  foliage  ;  (2)  as  regards  the  structure  of  the  carpel- 
late  cones,  whose  scales  are  opposite  instead  of  being  distributed  spirally, 
and  present  other  peculiarities  of  structure  and  habits  of  ripening  ;  (3)  with 
reference  to  the  special  characteristics  of  the  stamens.  These  genera  pre- 
sent a  higher  type  of  gymnosperm  evolution  in  these  respects  tlian  the  pine. 
Certain  cedars  (Cupressus)  are  equally  good  for  this  comparative  study. 

THE  ANGIOSPERMS,  OR  ANGIOSPERM.^ 

140.  The  morphology  of  the  angiosperms.  Tlie  general  morphol- 
ogy of  the  angiosperms,  including  roots,  stems,  leaves,  tiowerS; 
and  fruits,  together  with  many  ])rinciples  of  plant  physiology, 
have  been  treated  in  Tart  I,  The  Structure  and  Physiology  of 


160  TYPE  STUDIES 

Seed  Plants.  The  outlines  presented  here  will  deal  entirely 
with  the  gametophyte  generations  and  the  organs  of  the  sporo- 
phyte,  stamens  and  pistil  (composed  of  carpels),  especially  con- 
cerned with  their  development.  For  outlines  covering  general 
flower  structure  see  Sees.  44-46.  An  outline  for  a  general  type 
study  of  an  angiosperm  such  as  the  lily  is  presented  in  Sec.  162. 

141.  The  lily  studied  with  reference  to  its  gametophytes  (App.  22).  The 
lily  is  a  favorite  subject  for  the  study  of  pollen  formation  and  the  develop- 
ment and  fertilization  of  the  embryo  sac,  partly  for  its  clearness  and  partly 
for  the  relative  ease  with  which  material  may  be  obtained.  Other  types  of 
the  lily  family,  such  as  the  trillium,  the  tulip,  the  Koman  hyacinth,  etc., 
are  also  good.  Satisfactory  studies  on  the  gametophytes  of  the  angiosperms 
require  microtome  sections  of  the  structures  involved.  Directions  for  the 
preparation  of  these  are  outlined  in  Sec.  212.  The  wild  lilies,  such  as 
Lilium  philadelphicum,  furnish  excellent  material,  but  various  cultivated 
lilies  are  equally  good  or  better. 

A.  The  stamen  of  the  lily.    Dissect  away  the  perianth  of  the  lily  flower  to 
show  the  stamens  and  pistil. 

1.  Observe  the  arrangement  of  the  stamens  around  the  pistil.  Draw 
a  stamen  to  show  the  stalk  (filament)  and  the  attachment  of  the 
anther. 

2.  Note  how  the  pollen  is  discharged  from  the  anther, 

3.  Draw  a  pollen  grain  under  li.p.  to  show  the  markings  on  its  wall. 

4.  Section  the  anthers  and  observe  that  the  pollen  is  developed  in  four 
locules,  or  pollen  sacs,  running  lengthwise  of  the  anther. 

5.  In  microtome  sections  properly  stained  (Sec.  212)  note  that  the  pollen 
grains  will  show  a  large  central  nucleus,  tube  nucleus,  and  at  one  end 
the  generative  nucleus,  which  gives  rise  later  to  two  sperm  nuclei. 

B.  The  development  of  pollen.  To  obtain  the  stages  of  pollen  formation 
anthers  must  be  taken  from  very  young  unopened  buds,  the  stamens 
of  which  when  cut  across  exude  a  watery  fluid  from  the  pollen  sacs. 
Should  the  fluid  be  milky  or  yellowish  the  stamen  is  too  old  and  will 
certainly  contain  pollen  grains.  Stamens  of  the  proper  age  must  be 
fixed,  imbedded,  and  cut  lengthwise  on  the  microtome  and  stained  as 
described  in  Sec.  199,  D.  Such  preparations  will  show  various  stages  in 
development  and  division  of  the  pollen  mother  cells  to  form  the  pollen 
grains  in  groups  of  four,  or  tetrads.  The  following  consi)icuous  stages 
are  likely  to  be  found  and  should  be  drawn. 

1.  The  spore  mother  cells  before  division,  with  tlieir  nuclei  in  a  resting 
condition.    They  constitute  a  spore-forming  tissue  (archesporium), 


THE   LILY  161 

and,  increasing  in  size,  gradually  round  off  and  separate  from  one 
another. 

2.  Synapsis,.  ?i  veiy  common  stage  in  which  the  chromatin  within  the 
nucleus  of  the  spore  mother  cell  will  be  found  collected  in  a  dense 
mass,  generally  near  the  nucleolus  at  one  side  of  the  nucleus. 
Synapsis  is  a  very  important  stage,  since  it  appears  to  be  charac- 
teristic of  the  time  when  the  sporophyte  number  of  chromosomes  is 
reduced  by  half  to  the  number  of  the  gametophytes  (see  Principles, 
Sec.  334).  The  gametophyte  number  of  chromosomes  in  the  lily  is 
twelve,  and  first  appears  in  the  nuclear  divisions  within  the  pollen 
mother  cell  and  the  embryo  sac  (I),  3). 

3.  The  first  nuclear  division,  or  mitosis,  where  a  large  spindle  will 
be  found  within  the  spore  mother  cell,  and  the  chromosomes  will 
be  either  at  the  center,  forming  the  equatorial  plate  (see  Principles, 
Fig.  302,  B),  or  separated  into  two  groups  of  daughter  chromosomes 
that  pass  to  the  poles  of  the  spindle. 

4.  Two  daughter  nuclei  in  a  resting  condition  following  the  fii-st  mitosis 
and  the  division  of  the  spore  mother  cell  into  two  daughter  cells. 

5.  The  second  nuclear  division,  or  mitosis,  in  which  two  spindles  are 
formed  simultaneously  in  the  two  daughter  cells,  resulting  in  four 
daughter  nuclei. 

6.  The  final  division  of  the  spore  mother  cell  into  four  daughter  cells, 
forming  a  tetrad,  each  of  which  becomes  a  pollen  grain. 

The  processes  of  pollen  formation  are  identical  in  all  essentials  with  those 
of  spore  formation  in  the  bryophytes  and  pteridophytes,  and  show  that  the 
pollen  grains  are  microspores,  —  a  conclusion  sustained  by  their  further  de- 
velopment into  reduced  male  gametophytes.  The  pollen  sac  is  therefore  a 
microsporangium  and  the  stamen  a  microsporophyll.  Pollen  formation  in  the 
lily  and  related  types  is  an  attractive  subject  for  the  study  of  nuclear  and 
cell  division  in  the  higher  plants. 

C.    The  pistil  of  the  lily.    Draw^  the  pistil  in  side  view,  showing  : 

1.  The  ovule  case,  or  ovary,  below;  the  style  above,  bearing  the  three- 
lobed  stigma,  or  receptive  region,  for  the  pollen.  Note  that  the  ovule 
case  is  three-angled,  and  the  position  of  the  angles  with  reference 
to  the  lobes  of  the  stigma. 

2.  Cut  sections  of  the  ovule  case  both  from  flowers  which  have  recently 
opened  and  from  those  whose  perianth  has  been  withered  several 
days.  Under  l.p.  note  the  three  lucules,  or  chambers,  of  the  ovule 
case  and  the  ovules  within  them.  Show  their  i)()sition  in  an  outline 
drawing. 

The  three  locules  of  the  ovule  case  and  the  three  lobes  of  tlu'  slignui 
present  evidence  that  three  carpels  are  involved  in  the  formation  (»f  this 


162  TYPE   STUDIES 

pistil.    That  the  carpels  are  megasporophylls  is  proved  by  the  structure  and 

development  of  the  ovules  (see  U). 

D.  The  development  of  the  ovule  and  embryo  sac.  These  can  best  be  stud- 
ied from  microtome  cross  sections  of  the  ovule  cases  prepared  as 
described  in  Sec.  212.  The  ovule  cases  from  open  flowers  contain 
mature  embryo  sacs.  Those  collected  from  three  to  four  days  after  polli- 
nation may  show  stages  in  fertilization  (the  time  varies  in  different 
lilies).  Stages  in  the  development  of  the  embryo  sac  must  be  sought 
in  unopened  buds  along  with  or  somewhat  later  than  stages  in  pollen 
formation.  The  following  stages  are  likely  to  be  found  in  material  of 
graduated  ages  and  should  be  drawn : 

1.  Young  ovules  with  the  two  integuments  beginning  to  develop  around 
the  nucellus.  The  end  of  the  nucellus  will  be  exposed,  and  at  the 
tip,  under  a  layer  of  cells,  is  to  be  found  a  large  cell  with  deeply 
staining  protoplasmic  contents  and  conspicuous  nucleus.  This 
becomes  the  embryo  sac. 

2.  Later  stages  show  the  inner  integument  grown  beyond  the  nucellus 
and  forming  the  micropyle  at  the  tip  of  the  ovule.  The  outer 
integument  extends  around  on  the  outside  nearly  to  the  end  of  the 
inner  integument. 

3.  The  embryo  sac,  gradually  enlarging  with  the  growth  of  the  ovule, 
is  the  seat  of  three  nuclear  divisions,  or  mitoses,  by  which  the  number 
of  nuclei  is  increased  to  eight.  The  gametophyte  number  of  chromo- 
somes, twelve,  appears  in  the  first  of  these  mitoses  as  in  the  pollen 
mother  cell  (B,  2).  The  first  two  of  these  mitoses  have  peculiarities 
(see  Principles,  Sec.  3()0  and  footnote)  which  show  that  they  are  of 
the  same  kind  as  those  characteristic  of  pollen  formation  and  spore 
formation  when  tetrads  are  developed  within  mother  cells.  But 
tetrads  are  no  longer  developed  in  the  nucellus  of  the  lily,  although 
present  in  the  ovules  of  many  other  angiosperms  (see  Principles, 
Fig.  304).  The  four  nuclei  resulting  from  the  first  two  mitoses  in 
the  embryo  sac  of  the  lily,  although  comparable  to  megaspore 
nuclei,  have  all  become  included  in  the  very  much  reduced  female 
gametophyte  that  is  developed  in  the  embryo  sac. 

4.  The  eight  nuclei  of  the  mature  embryo  sac  become  distributed  as 
follows  :  (a)  three  nuclei  form  the  egg  apparatus  at  the  micropylar 
end  of  the  sac,  one  being  the  egg  nucleus  and  lying  slightly  below 
and  between  the  other  two,  which  are  termed  synergids ;  (b)  three 
nuclei  fonn  the  group  of  antipodal  nuclei  at  the  opposite  end  of  the 
sac ;  (c)  the  other  two,  called  polar  nuclei,  approach  one  another  in 
the  center  of  the  sac.  This  is  the  structure  of  the  mature  female 
gametophyte  (see  Principles,  Fig.  306,  B). 


POLLEN   (iRAIX   OF    ELDER  163 

The  first  two  mitoses  in  tlie  embryo  sac  of  tlie  lily  show  that  it  is  a  mega- 
spore  mother  cell  in  this  plant  (as  also  in  related  types),  which  later  contains 
the  female  gametophyte.  The  nucellus  is  therefore  a  megaaporangium  and 
the  carpel  a  megasporophyll. 

E.  Fertilization  and  double  fertilization.  Stages  showing  the  nuclear  fusions 
of  fertilization  and  double  fertilization  are,  of  course,  not  common,  but 
one  preparation  will  serve  for  a  demonstration  of  the  processes.    The 
pollen  tube  brings  two  sperm  nuclei  into  the  embryo  sac.    One  of  the.se 
unites  with  the  egg  nucleus.,  fertilizing  it,  and  the  other  unites  with  the 
two  polar  nuclei,  forming  a  triple  fusion  which  results  in  the  large 
endosperm  nucleus  in  the  center  of  the  sac  (see  Principles.,  Fig.  307). 
E.    The  development  of  the  embryo  and  endosperm.    The  fertilized  egg 
nucleus  with  surrounding  protoplasm  becomes  tlie  fertilized  egg,  and, 
forming  a  cell  wall  about  itself,  proceeds  to  develop  the  embryo  sporo- 
phyte  at  the  micropylar  end  of  the  embryo  sac.    The  endosperm  nucleiLS 
gives  rise  through  successive  divisions  to  a  very  large  number  of  nuclei, 
which  become  distributed  in  the  layer  of  protoplasm  which  lines  the  em- 
bryo sac  (see  Principles,  Fig.  308).    Cell  walls  are  later  formed  between 
these  nuclei,  and  the  embryo  sac  becomes  filled  with  a  delicate  tis.sue 
called  the  endosperm,  in  which  the  developing  embryo  lies  imbedded. 
It  is  important  to  note  that  the  endosperm  of  all  the  angiosperms  is  a 
development  following  fertilization  and  therefore  not  strictly  comparable 
to  the  endosperm  of   gymnosperms,   as  illustrated  in  the  pine,  which  is 
formed  before  fertilization  and  is  therefore  strictly  gametophytic  in  charac- 
ter without  the  complication  of  double  fertilization  on  the  union  of  polar 
nuclei.    The   group  of  three  antipodal  nuclei  in   the  embryo  sac  of  the 
angiosperms  may  represent  the  endosperm  of  gymnosperms,  but  this  is  not 
fully  established.    The  female   gametophyte  of  the  angiosperms  is  much 
simpler  than  that  of  the  gymnosperms,  having  only  eight  nuclei,  one  egg,  and 
no  clearly  defined  archegonium.    The  male  gametophyte  of  the  angiosperms 
is  likewise  simpler,  containing  only  three  nuclei,  two  sperm  nuclei,  and  the 
tube  nucleus. 

142.  The  pollen  grain,  or  microspore  of  the  elder.  Some  pollen  grains  at 
maturity  contain  the  male  gametophytes  much  further  advanced  than  is 
shown  in  those  of  the  lily.  This  is  well  illustrated  in  the  elder  {Sambucus). 
Unopened  stamens  should  be  fixed  and  preserved  in  alcohol.  The  anthers  of 
such  may  be  teased  apart  in  water,  allowing  the  pollen  grains  to  escape. 
When  stained  with  eosin  these  grains  will  be  seen  to  contain  three  nuclei,  a 
tube  nucleus  lying  freely  in  the  center  of  the  cell,  and  two  sperin  nuclei 
somewhat  at  one  side,  surrounded  by  denser  protoplasm,  forming  two  male 
cells  (.see  Principles,  Fig.  306).  The  nuclear  divisions  are  completed  in  this 
male  gametophyte  at  the  time  the  pollen  is  shed,  and  the  only  further 


164  TYPE   STUDIES 

development  is  that  of  the  pollen  tube,  which  carries  the  sperm  nuclei  to  the 
embryo  sac.  Microtome  sections  of  the  ripe  anthers  of  the  elder  (Sec.  212) 
will  give  excellent  preparations  of  this  interesting  condition. 

The  pollen  grains  of  many  plants,  as  the  lily,  contain  but  tw^o  nuclei  at 
the  time  of  pollination.  These  are  the  tube  nucleus,  above  mentioned,  and 
the  generative  nucleus,  which  later  gives  rise  to  the  two  sperm  nuclei. 

143.  Capsella,  the  shepherd's  purse,  studied  for  the  development  of  the  flower, 
ovule,  pollen  tube,  and  embryo  (App.  23).  The  shepherd's  purse  is  in  many 
respects  an  excellent  type  for  a  general  study  of  a  dicotyledonous  seed 
plant,  although  the  flower  is  rather  small.  It  is  a  particularly  good  subject 
for  the  study  of  the  topics  indicated  in  the  above  heading. 

A.  The  development  of  the  flower.  Tease  apart  in  a  drop  of  water,  under 
a  dissecting  microscope,  the  extreme  tip  of  a  flower  cluster  (which  is  a 
raceme),  to  obtain  the  youngest  flowers  (microscopic)  just  below  the 
growing  point.  Older  stages  may  be  cleared  by  adding  potash  solution 
if  necessary  (Sec.  160).    Search  for  the  following  stages  and  draw  : 

1.  The  young  flowers  appearing  as  small  protuberances  just  back  of  the 
growing  point. 

2.  A  circle  of  sepals  developing  at  the  tip  of  the  young  flower. 

3.  The  growth  of  the  sepals  over  the  tip  of  the  flower  and  the  origin  of 
the  stamens  in  a  circle  within. 

4.  The  development  of  two  carpels,  more  or  less  united  below,  at  the 
tip  of  the  flower. 

5.  The  late  appearance  of  the  petals  between  the  sepals  and  stamens, 
after  all  the  other  parts  of  the  flower  are  present. 

6.  The  final  folding  one  over  the  other  of  the  sepals  in  the  young  bud, 
the  growth  of  the  petals,  the  differentiation  of  the  stamens  into 
anthers  and  stalks  (filaments),  the  union  of  the  carpels  above  to  form 
the  pistil,  with  the  ovule  case  or  ovary  below,  in  which  the  ovules  ap- 
pear as  outgrowths  along  the  surface. 

7.  Microtome  sections  cut  lengthwise  of  the  tip  of  the  raceme  (Sec.  212) 
give  excellent  stages  in  the  development  of  the  flowers,  and  especially 
the  closing  together  of  the  carpels  to  form  the  pistil  and  the  origin 
of  the  ovules  along  their  inner  surface  within  the  ovule  case. 

B.  The  development  of  the  ovule.  Pick  to  pieces  some  of  the  youngest 
flowers  that  can  be  easily  seen  with  the  unaided  eye.  Open  the  ovule 
cases,  or  ovaries,  in  a  drop  of  water,  with  the  point  of  a  needle,  thus 
exposing  the  ovules.  A  variety  of  stages  will  be  presented.  Search  for 
the  following  and  draw : 

1.  The  young  ovule,  consisting  of  the  nucellus  at  the  end  of  a  short 
stalk,  with  the  two  integuments  just  beginning  to  appear  like  collars 
at  its  base, 


CAPSELLA 


Kio 


2.  A  stage  in  which  the  integuineiits  are  further  (h-vclopud,  tlie  outer 
arising  somewhat  below  the  inner  one.  The  large  cmhn/n  sac  is  gener- 
ally evident  at  this  time  in  the  center  of  the  nueellus. 

3.  A  stage  in  which  the  outer  integument  has  grown  over  and 
beyond  the  inner  one,  so  that  only  the  extreme  tip  of  the  nueellus 
is  seen.  At  tliis  time  the  ovule  begins  to  bend  over  at  its  basal 
region. 

4.  Finally  the  outer  and  inner  integuments  'grow  completely  over  the 
nueellus,  almost  meeting  beyond  to  form  the  small  opening  called 
the  ynicropyle.  Meantime  the  bending  of  the  ovule  brings  the^'micro- 
pyle  close  to  the  stalk  of  the  ovule,  so  that  the  latter  is  therefore 
completely  bent  on  itself  (campylotropous)..  This  condition  will  be 
found  in  the  ovules  of  rather  young,  unopened  flowers,  and  such 
preparations  may  be  cleared  with  potash. 

C.  ^  The  development  of  the  pollen  tubes.  Mount  the  pistil  of  an  open  flower 
in  water  and  examine  the  stigma  under  m.p.  Note  the  papillce  on  its 
surface,  and  among  the  papillae  the  germinating  pollen  grains,  which 
will  be  found  sending  tubes  into  the  tissue  of  the  stigma.  Clear  with 
potash  if  too  opaque.    Draw. 

D.  The  development  of  the  embryo.  Remove  the  pistils  from  flowers,  the 
petals  of  which  have  begun  to  wither.  Open  the  ovule  case  with  a 
needle  and  mount  the  ovules  in  a  potash  solution.  The  embryo  may 
sometimes  be  clearly  seen  lying  in  the  embryo  sac.  Press  gently  on  the 
cover  glass  and  the  embryo  will  be  crushed  or  squeezed  out.  Note  the 
row  of  cells  forming  the  siispensor,  the  lower  one  of  which  is  much 
enlarged.  Make  a  number  of  preparations  of  younger  and  older 
ovules,  which  are  likely  to  show  the  following  stages,  and  should  be 
drawn  : 

1.  The  suspensor  before  the  formation  of  the  embryo,  consisting  of  a 
filament  attached  by  a  large  basal  cell  near  the  micropylar  end  of 
the  embryo  sac. 

2.  The  development  of  the  embryo,  beginning  at  the  free  end  of  (he 
suspensor,  by  the  formation  of  walls  in  three  planes,  thus  diltVren- 
tiating  a  globular  structure. 

3.  The  later  growth  of  the  embryo,  with  the  appearance  of  two  cotyle- 
dons, and  the  development  of  the  root  at  the  point  where  the  embryo 
is  attached  to  the  suspensor. 

4.  Lengthwise  microtome  sections  of  the  ovules  (Sec.  212)  will  show 
the  relation  of  the  developing  embryo  to  the  enlarged  and  cur\ed 
embryo  sac  with  its  endosperm,  and  the  integuments  of  the  ovule 
(see  Principles,  Fig.  309,  H). 


166  TYPE  STUDIES 

Part  II  of  this  manual  presents  a  series  of  type  studies  fur- 
nishing an  outline  of  the  comparative  morphology  and  life 
histories  of  plants,  upon  which  are  based  systems  of  classifica- 
tion and  various  theories  of  the  evolution  of  the  groups.  While 
botanists  are  in  general  agreement  on  the  principal  lines  of 
plant  evolution  and  in  full  accord  as  to  the  fact  that  there  has 
been  an  evolution,  the  details  of  the  history  of  development 
must  always  remain  speculative  problems  for  the  reason  that 
evolutionary  processes  have  been  in  force  since  very  early  geo- 
logical ages  and  the  records  of  plant  life  in  former  periods,  pre- 
served as  fossil  remains,  are  relatively  scanty.  Consequently, 
while  it  is  often  of  great  interest  to  draw  or  diagram  lines  of 
plant  evolution  indicating  relationships  of  groups,  such  outlines 
should  generally  be  considered  as  provisional  attempts  to  help 
forward  discussion  rather  than  as  expressions  of  final  judgment. 

Such  a  study  of  comparative  morphology  as  may  be  framed 
from  the  matter  presented  in  Parts  I  and  II  forms  an  excellent 
foundation  for  detailed  work  in  plant  physiology  and  the  funda- 
mentals of  ecology.  Indeed,  it  may  be  said  to  be  essential  to 
extended  work  in  these  subjects,  for  a  knowledge  of  structure 
must  always  precede  a  study  of  functions  and  life  activities. 

When  a  course  in  botany  is  planned  to  begin  with  type  studies 
such  as  may  be  chosen  from  Part  II,  the  usual  procedure  would 
be  to  supplement  or  end  the  course  with  the  more  special  exam- 
ination of  the  seed  plants.  These  latter  studies  may  be  not  only 
morphological  and  physiological  but  also  ecological,  and  would 
involve  a  selection  of  such  topics  and  experiments  from  Parts  I 
and  III  as  seem  best  suited  to  the  conditions  under  which  the 
work  must  be  given. 

Note  carefully  the  fact  that  the  order  of  topics  in  Part  III 
merely  follows  that  of  Part  III  of  the  authors'  Frinciples  of  Botany. 
The  teacher  must  shape  the  order  of  treatment  for  himself, 
choosing  such  a  sequence  as  may  best  meet  the  seasonal  succes- 
sion of  plant  forms  and  of  phenomena  of  plant  life  out  of  doors. 


Part  III 

ECOLOGY 

PARASITIC  AND  CARNIVOROUS  PLANTS 

144.  Field  study  of  parasites. 

A.  Study  out  of  doors  any  parasitic  seed  plants  that  you  can  find. 
In  most  parts  of  the  country  tlie  dodders  are  of  much  more  fre- 
quent occurrence  than  any  other  parasites  among  the  higher  plants. 
Frequently  several  species  of  dodder  can  be  found. 

Note  and  collect  the  host  plants  on  which  the  parasite  grows  and 
observe  the  mode  of  attachment  between  parasite  and  host.  Find  out 
whether  the  host  is  at  all  injured  by  the  parasite. 

B.  If  possible  transplant  thriving  specimens  of  the  parasite  upon  new 
kinds  of  host  and  see  whether  they  will  grow  there.  Collect  seeds  of 
any  parasitic  plants  found,  germinate  the  seeds,  and  make  studies  of 
the  behavior  of  their  seedlings.   Are  the  seedlings  green  at  first  ? 

Reference.    Kerner-Oliver,  2. 

145.  Field  study  of  carnivorous  plants. 

A.  Examine  any  carnivorous  plant  which  you  can  find  growing  sponta- 
neously (various  species  of  Drosera  and  Sarracenia  are  the  kinds  most 
widely  distributed).  Make  notes  on  the  total  number  of  insects  cap- 
tured by  a  single  plant  and  by  a  single  leaf. 

B.  In  the  case  of  Drosera  study  and  draw  various  leaves,  some  expanded 
and  some  closed  over  insects. 

C.  Put  into  50  per  cent  alcohol  or  2-4  per  cent  formalin  solution  all  the 
insects  obtained  from  any  one  kind  of  carnivorous  plant  and  bring 
them  to  the  laboratory  for  determination  of  the  groups. 

146.  Laboratory  study  of  carnivorous  plants. 

A.  Put  living  flies  in  the  pitchers  of  Sarracenia  containing  their  usual 
amount  of  liquid,  and  note  whether  any  of  the  flies  escape,  or  what 
finally  becomes  of  them. 

B.  Feed  leaves  of  Drosera  with  bits  of  raw  meat,  particles  of  cheese,  veiy 
small  insects,  bits  of  sand,  or  broken  glass.    Place  the  objects  very 

167 


168  ECOLOGY 

carefully,  on  the  tips  of  the  glandular  hairs,  note  what  movements,  if 
any,  occur,  make  sketches  of  the  leaf  in  various  positions,  and  keep  a 
complete  daily  record  of  the  behavior  of  the  leaf  until  it  returns  to  its 
ordinary  form. 

References  for  Sees.  145,  146.    Darwin,  64  ;  Darwiu  and  Acton,  11. 

HOW  PLANTS  PROTECT  THEMSELVES  FROM  ANIMALS 

147.  Field  study.  If  possible,  visit  pastures  grazed  by  horses,  cattle,  or 
sheep,  and  large  barnyards  where  weeds  are  abundant.  Make  a  sketch  map 
of  a  small  part  of  the  pasture  or  barnyard,  showing  the  clumps  of  weeds 
that  have  been  left  uneaten  ;  number  the  clumps,  and  at  the  bottom  of  the 
map  indicate  what  plants  make  up  each  group.  Study  the  characteristics  of 
some  plants  that  are  not  usually  eaten,  and  state  the  most  obvious  means  of 
protection  of  each  plant. 

148.  Laboratory  study.  Examine  in  detail  any  of  the  plants  of  your  region 
which  are  left  unharmed  by  grazing  animals,  and  make  out  a  tabular  list 
of  the  protective  equipment  of  each  plant.  Use  the  microscope  to  study 
and  make  sketches  of  cutting  edges  of  grasses  and  sedges  and  the  rough  or 
stinging  hairs  or  spines  of  such  plants  as  mulleins,  nettles,  thistles,  and  so  on. 
Do  not  taste  plants  suspected  of  being  poisonous,  but  try  those  which  are 
known  not  to  be  so.  If  some  plants  are  attacked  by  insects,  though  not  by 
grazing  quadrupeds,  make  a  note  of  it.  Record  the  notes  in  a  table  like 
the  one  on  the  following  page.i 


POLLINATION  OF  FLOWERS 

149.  Studies  in  insect  pollination.*  *  The  student  cannot  gather  more  than 
a  very  imperfect  knowledge  of  the  details  of  cross  pollination  in  flowers  with- 
out actually  watching  some  of  them  as  they  grow  and  observing  their  insect 
visitors.  If  the  latter  are  caught  and  dropped  into  a  wide-mouthed,  stop- 
pered bottle  containing  a  bit  of  cotton  saturated  with  chloroform,  most  of 
them  may  be  identified  by  any  one  who  is  familiar  with  our  common  insects. 
The  insects  may  be  observed  and  classified  in  a  general  way  into  butterflies, 
moths,  bees,  flies,  wasps,  and  beetles,  without  being  captured  or  molested. 

Whether  these  out-of-door  studies  are  made  or  not,  several  flowers  should 
be  carefully  examined  and  described  as  regards  their  arrangements  for 
attracting  and  utilizing  insect  or  bird  visitors. 

1  it  will  probably  be  necessary  for  the  instructor  to  determine  for  the  student 
many  of  the  species  studied. 


ADAPTATIONS  FOR   POJ.LINATION 


169 


Means  of  Protp:ction  of  Certain  Plants 


^ 

i 

1 

1 

.11 

o 

p 

O 

fcp 

—   ;-i 

p 

o 

1 

o  Z 
1^  ^ 

JimsoR  weed  {Datura) 

X 

9 

X 

X 

References.    Kerner-Oliver,  2  :  Ludwig,  51. 


Outline  for  Study  of  Adaptations  for  Pollination^ 

r  1,  greenish,  nectarless,  inconspicuous  perianth  ? 
I.    Is  the  flower  I  2,  appearing  before  the  leaves  ? 

characterized  by    i  3,  dry,  dusty  pollen  ? 
I  4,  feathery  stigmas  ? 

If  several  of  these  characteristics  are  found,  it  is  probably  ivind-pollinated. 

r  5   curving  stamens  which  bring  the  anthers  into  oon- 
II.    Is  the  flower  I     '      ^^^^  ^^.^^^  ^j^^  ^^.^^^^  ,    If  ^^^  ;^  j,  self-pollinated 

characterized  by  |  ^^^^  Principles,  Fig.  330).^ 

i  Pollination  by  water  is  not  discussed  here,  as  the  cases  are  rather  few  and 
material  is  not  usually  available  for  study. 

2  Many  self-polliuated  tiowers  are  not  easily  distuiuuislied  as  such. 


170 


ECOLOGY 


III.  Is  the  flower 
characterized  by 


6,  odor  ? 

7,  color  (not  green)  ? 

8,  nectar  ? 

9,  sticky  pollen  ? 

10,  opening  during  only  part  of  the  day  ? 

11,  bilateral   symmetry  ? 

12,  facilities   for  insect  visitors  ?     (See   Principles, 
Figs.  324,  325.  )i 

13,  mechanism  for  holding  visitors  imprisoned  until 
covered  with  pollen  ? 

14,  mechanism  for  pollinating  visitors  ?    (See  Prin- 
ciples, Figs.  331,  332.)  1 

15,  two    or    three    lengths    of    stamens  and   pistils 
(dimorphism  or  trimorphism)  ? 

16,  unequal  maturing  of  stamens  and  pistil  (dichog- 
amy) ? 

If  any  of  these  characteristics  (III)  are  found,  the  flower  is  pollinated  by 
insects,  birds,  or  other  animals. 

Make  a  list  of  all  the  attractions  displayed  by  the  flower  examined,  and 
if  possible  find  out  what  visitors  it  receives  and  how  their  visits  are  utilized. 
'  17,  a  sticky  stem  or  flower  stalk  ? 

18,  water  reservoirs  along  the  stem  ? 

19,  a  slippery  flower  stalk  ? 

20,  a  sticky-hairy  or  slippery  nodding  calyx  ? 

21,  a  corolla  with  closed  throat  ? 

22,  stamens  or  pistils  covering  the  nectaries  ? 

23,  a  long  calyx  or  corolla  tube  ? 
[^  24,  long  spurs,  with  the  nectar  stored  at  the  bottom  ? 

Make  a  list  of  these  protections,  and  if  possible  study  their  operation. 

The  following  list  includes  a  considerable  number  of  the  most  accessible 
flowers  of  spring  and  early  summer,  about  which  it  is  easy  to  get  informa- 
tion from  books. 


Is  the  flower  under 
examination  pro- 
tected from  unde- 
sirable visitors  by 
means  of 


List  of  Insect-Pollinated  Flowers  ^ 

I 

1.  Flax Linum  usitatissimum Knuth 

2.  Missouri  currant .     .     .     Ribes  aureum Knuth 


1  For  very  many  other  devices  for  pollination  see  Knuth-Davis,   62,   and 
Kerner-Oliver,  2. 

2  The  plants  in  this  list  are  arranged  somewhat  in  the  order  of  the  complexity 
of  their  adaptations  for  insect  pollination,  the  simplest  first.  It  would  be  well  for 


ADAPTATIONS   FOR  POLLINATION 


171 


3.  Snowberry     .     . 

4.  Lilac     .... 

5.  Periwinkle     .     . 

6.  Mignonette    .     . 

7.  Lily  of  the  valley 

8.  Dead  nettle    .     . 

9.  Bleeding  heart    . 

10,  Columbine      .     , 

11.  Monkshood    .     . 


Symphoricarpus  racemosus     ....  Kinith 

Syringa  perslca Knuth 

Vinca  minor Knuth 

Reseda  odorata Kiuith 

Convallaria  majalis Knuth 

Lamium  album Lubbock 

Dicentra  (Diclytra)  spectabilis     .     .     .  Knuth 

Aquilegia  vulgaris Knuth 

Aconitum  Napellus Knuth 


12.  Larkspur  .     . 

13.  Herb  Robert . 

14.  Pink     .     .     . 

15.  Fireweed  .     . 

16.   "Nasturtium" 

17.  Pansy   .     .     . 

18.  Heal-all     .     .     . 

19.  Ground  ivy    . 

20.  Lousewort 

21,  Snapdragon   . 

22.  Iris  .... 

23.  Bellflower       . 

24.  Horse-chestnut 

25.  Yarrow 

26.  Oxeye  daisy 

27.  Dandelion 


II 

Delphinium  elatum,  D.  consolida     .     .     Knuth 

Geranium  robertianum Knuth 

Dianihus  (various  species)      ....     Knuth 

Epilobium  angustifolium Gray 

Tropmolum  majus    ....  Newell,  Lubbock 

Viola  tricolor Knuth 

Prunella  vulgaris Knuth 

Nepeta  hederacea      ....      Knuth,  Newell 
Pedicularis  canadensis      .     .      Knuth,  Newell 

Antirrhinum  niajus Knuth 

Iris  versicolor Newell 

Campanula  rapunculoides      ....     Knuth 
u^sculus  Hippocastanum Newell 

III 

Achillea  millefolium Knuth 

Chrysanthemum  Leucanthemum       .     .     Kiuith 
Taraxacum  officinale    .     •     •      Knuth,  Newell 


28.  Barberry  .     .     . 

29.  Mountain  laurel 


IV 

Berberis  vidgaris Lubbock 

Kalmia  latifoiia Gray 


each  student  to  take  up  the  study  of  the  arrangements  for  the  utilization  of  insect 
visitors  in  several  of  the  groups  above,  numbered  with  Roman  numerals.  Ex- 
planations of  the  adaptations  can  be  found  in  the  works  c'ite<l  by  abbreviations  at 
the  right.  Knuth  stands  for  Knuth-Davis's  Handbook  of  Floirer  PoUiiKition, 
62;  Lubbock,  for  British  Wild  Floioers,  considered  in  Relation  to  J/isects  :  Gray, 
for  Gray's  Structural  Botany;  and  Newell,  for  Miss  Newell's  Outlim'sof  Ljssons 
in  Botany,  Part  II.  Consult  also  Weed's  Ten  Nero  England  Blossoms,  and  Keruer- 
Oliver,  2.  The  instructor  may  tind  it  necessary  to  identify  most  of  the  species. 


172 


ECOLOGY 


30.  White  clover 

31.  Ked  clover 

32.  Locust  . 

33.  Wisteria 

34.  Vetch  . 

35.  Pea  .     . 

36.  Bean     . 

37.  Groundnut 


38.  Partridge  berry 

39.  Primrose   .     . 

40.  Loosestrife     . 


41.  Milkweed 


42.  Lady's  slipper 


V 

Tri folium  repens Kmith 

Trifolium  pratense Knuth 

Robinia  Pseudo-Acacia Gray 

Wisteria  sinensis Gray 

Vicia  Cracca Knuth 

Pisum  sativum Knuth 

Phaseolus  vulgaris .  Gray 

Apios  tuberosa Gray 

VI 

Mitchella  repens Gray 

Primula  grandijiora,  P.  officinalis  .      Lubbock 

Lythrum  Salicaria Gray 

VII 

Asclepias  Syriaca     ....     Knuth,  Newell 

VIII 

Cypripedium  acaule Newell 


HOW  PLANTS   ARE    SCATTERED   AND   PROPAGATED 


150.  Field  study  of  vegetative  propagation. 

A.  Collect,  by  digging  them  up,  sketch,  and  describe  any  underground 
stems  of  use  in  multiplying  plants.  There  are  many  rootstock-produ- 
cing  species,  such  as  June  grass,  quick  grass,  Bermuda  grass,  Canada 
thistle,  common  sorrel  {Rumex  Acetosella),  wild  iris,  wild  ginger,  sweet 
flag,  various  sunflowers,  and  some  mints.  If  possible  dig  away  the 
earth  from  one  side  of  a  hill  of  potatoes,  and  sketch  some  of  the  roots, 
subterranean  branches,  and  tubers.  Bulbs  are  borne  by  a  large  pro- 
portion of  the  members  of  the  lily  family. 

Make  sketches  to  illustrate  the  spread  of  plants  by  rooting  branches, 
as  in  the  raspberiy,  strawberry,  and  cinquefoils. 
In  any  cleared  or  partially  cleared  bit  of  woodland  note  the  way  in 
which  some  trees  produce  a  crop  of  sprouts  from  the  stump. 
Examine  the  neighborhood  of  black  locust  trees  (Robinia),  silver- 
leaved  poplars,  or  balm  of  Gilead  poplars,  to  find  out  how  far  these 
trees  "spread  by  the  root."  Dig  up  a  young  sprout,  with  a  piece  of 
the  parent  root,  and  sketch  it. 

Reference.    Beal,  63, 


B 


D 


DISSEMINATION   OF   SEEDS  173 

151.  Laboratory  study  of  vegetative  propagation. 

A.  In  moist  earth  or  sand  plant  pieces  of  potato  tubers,  each 
containing  one  or  more  "  eyes,"  and  others  without  eyes. 
Note  results  and  sketch  any  plants  that  are  produced. 

B.  Plant  bulbs  and  bulblets  of  onion  and  note  the  compara- 
tive growth  of  the  plants  produced. 

C.  In  sand  which  is  kept  moist  plant  cuttings  of  any  of  the 
following  plants  :  "geranium,"  Trao?esca7i^m,  willow,  cotton- 
wood,  currant,  raspberry,  blackberry,  and  grapevine.  When 
the  cuttings  have  rooted,  sketch  some  of  them,  and' decide 
whether  the  roots  spring  indifferently  from  any  part  of 
the  stem. 

D.  If  obtainable,  put  some  vigorous  Bryophijlhim  leaves  on 
moist  sand,  cover  with  a  bell  glass,  and  sketch  the  leaf  with 
young  plants,  if  any  appear. 

152.  Field  study  of  dissemination  of  seeds. 

A.  Examine  the  region  about  any  tree  or  shrub  which  has  no  near 
neighbors  of  its  own  kind,  and  try  to  trace  tlie  distance  to  which  its 
seeds  have  been  carried.  In  case  enoiigli  seedlings  are  found  to  war- 
rant it,  make  a  map  to  show  their  distribution  with  reference  to  the 
parent  tree. 

B.  Discuss  the  means  by  which  the  seeds  have  been  carried. 

C.  Watch  such  trees  as  elms,  maples,  lindens,  willows,  sycamores,  and 
cottonwoods,  when  the  fruits  or  seeds  are  fully  ripe,  and  find  out  how 
far  they  travel.  What  trees  hold  many  of  their  seeds  after  they  are 
fully  ripe  ?    What  are  the  advantages  of  this  ? 

D.  Look  for  as  many  contrivances  for  seed  dispersal  as  possible,  ami 
classify  the  plants  studied  into  those  with  fruits  or  seeds  dispersed  : 

(1)  by  wind. 

(2)  by  water. 

(3)  by  animals. 

(4)  by  some  contrivance  for  shooting  or  slinging  the  seeds. 

Referenck.    Kerner-Oliver,  2. 

153.  Laboratory  study  of  dissemination  of  seeds. 

A.  Find  out  which  of  the  wind-carried  fruits  and  seeds  fall 
most  slowly  from  the  laboratory  ceiling  to  the  floor. 


174  ECOLOGY 

B.  Test  some  of  the  following  water-carried  fruits  and  seeds 
to  see  which  will  float  longest :  aquatic  grasses,  rushes,  and 
sedges,  polygonums,  water  dock,  bur  reed,  arrowhead,  water 
plantain,  pickerel  weed,  alder,  buttonbush,  water  parsnip 
(SiuDi),  water  hemlock  (Cicuta),  water  pennywort  {Hijdro- 
cotyle),  lotus  {Nelumho). 

C.  Sketch  and  describe  in  detail  the  fruit  or  seed  which 
appears  to  be  best  adapted  to  each  of  the  four  modes  of  dis- 
persal above  mentioned  (Sec.  152,  D). 

COMPETITION  AND  INVASION 

164.  Field  study  of  competition. 

A.  Find  a  spot  in  which  many  weed  seedlings  have  sprung  up,  stake  off 
one  or  two  square  feet,  count  the  plants,  and  then  watch  their  growth 
for  as  long  a  period  as  possible.  Stake  off  a  similar  plot,  pull  up  all 
but  one  or  two  of  the  weeds,  and  compare  the  growth  of  these  plants 
with  that  of  the  crowded  ones. 

B.  Beginning  as  soon  as  weed  seedlings  start  in  the  spring,  stake  off  a 
square  foot  of  very  weedy  ground,  pull  up  and  count  all  the  seedlings 
which  grow  on  the  plot,  continue  the  count  as  others  spring  up,  and 
make  a  list  of  the  kinds  obtained  i  and  the  total  number  of  each  kind. 

C.  Allow  any  large,  vigorous  weeds  to  grow  up  among  lettuce,  radish, 
carrot,  or  other  seedlings,  and  notice  which  set  of  plants  prevails. 
Give  as  many  reasons  as  possible  for  this  result. 

References.    Clements,  50  ;  Principles^  Chapter  XXXIV. 

155.  Field  study  of  invasion.*  * 

A.  Look  for  places  in  which  pastures  or  mowing  fields  are  beginning  to 
"  run  out,"  and  daisies  {Chrysanthemum)^  sorrel  (Rumex),  cone  flowers, 
and  similar  weeds  are  taking  the  place  of  the  grass. 

Look  for  a  lawn  that  is  too  much  shaded  and  becoming  filled  with 
chickweed  or  other  weeds. 

B.  Find  a  pond  in  process  of  drying  up  and  notice  what  changes  are 
taking  place  in  the  character  of  the  vegetation. 

C.  Study  an  abandoned  strawberry  bed. 

D.  Examine  a  clearing  in  which  young  saplings  have  begun  to  grow  to  a 
height  of  15  or  20  feet.  In  every  case  make  a  list  of  the  older  inhabit- 
ants of  the  territory  i  and  of  the  newcomers  i  and  give  as  many  reasons 

1  Identified  by  the  instructor. 


ECOLOGICAL  CLASSES  175 

as  possible  for  the  prevalence  of  the  latter.    State  what  would  prob- 
ably be  the  condition  of  the  piece  of  ground  examined  if  left  unmo- 
lested for  ten  years  or  more. 
Kkfekences.    Clements,  59  ;  Principles,  Chapters  XXXIV,  XXXV. 

PLANT  SUCCESSIONS 

156.  Field  study  of  successions. 

A.  p:xamine  a  field  of  wheat,  rye,  oats,  or  barley,  when  the  grain  is  not 
more  than  a  foot  high,  again  when  it  is  ready  for  reaping,  and  finally 
as  long  as  possible  after  reaping,  before  fall  plowing  or  frost  destroys 
the  plants  upon  it.  Make  a  list  of  all  the  plants  that  can  be  recog- 
nized at  each  period,  and  note  which  ones  are  in  blossom  or  in  frait. 

B.  Study  wood  lots  with  full-grown  trees  upon  them,  others  from  which 
the  trees  have  recently  been  cut  off,  others  still  which  have  been 
cleared  for  many  years.  Make  a  general  statement  of  the  kinds  and 
relative  numbers  of  seed  plants  of  all  sorts  found  in  each  case. 

C.  If  possible,  study  the  changes  in  the  vegetation  of  old  fields  allowed 
to  grow  up  to  weeds  and  bushes. 

Draw  up  a  general  account  of  what  you  have  found  to  be  the  order 
of  succession  of  plants  in  grain  fields,  in  cleared  woodland,  and  in 
abandoned  fields.  Try  to  give  some  reasons  why  the  plants  succeed 
one  another  in  the  order  actually  observed. 
liKFERENCES.  Clcments,  59;  Schimper-Fisher,  56;  Warming-Groom- 
Balfour,  57  ;  Principles,  Chapter  XXXV. 


ECOLOGICAL  CLASSES 

157.  Field  study  of  ecological  classes.** 

A.  Examine  the  vegetation  of  any  accessible  lake,  pond,  marsh, 
or  river,  of  ordinary  woods,  thickets,  and  grass  lands,  and 
of  the  driest  areas  in  the  region,  such  as  sand  hills  or  dunes, 
barren  knolls  or  banks,  ledges  or  outlying  masses  of  rook. 
Select  some  of  the  typical  inhabitants  of  each  region  and 
make  a  list  of  : 

,.    „    ,       ,  ( (ct)  living  only  in  water. 

(1)  Hydrophytes^  ^  \.   .        .  /    .         ,         •  ^     •, 
^  ^      -^       ^  -^        [(^>)  hvmg  either  in  water  or  in  very  wet  sou 

(2)  Mesophytes. 

(3)  Xerophytes. 


176  ECOLOGY 

Describe  the  characteristics   of  each  group,   giving  atten- 
tion to  all  the  vegetative  parts  of  the  plant  body. 

B.  In  woods  or  thickets  make  lists  of  the  sun  plants  and  shade  plants, 
and  classify  the  trees  roughly  as  regards  their  tolerance  of  shade  con- 
ditions. Measure  the  relative  illumination  of  some  of  the  plants  which 
live  in  the  deepest  shade  by  the  method  given  in  Exp.  XXVIII. 

C.  Study  the  distribution  of  plants  as  related  to  the  character  of  the 
soil,  looking  for  species  characteristic  of  limestone  and  of  sandy  soils. 
If  possible,  find  assemblages  of  plants  in  loose  sand,  especially  of  sand 
dunes,  and  report  on  their  peculiar  form  and  habits.  If  there  are 
accessible  localities  for  halophytes,  examine  the  vegetation  of  salt 
marshes,  of  the  sea  beach,  or  of  "  alkali "  lands,  and  describe  some  of 
the  most  noticeable  characteristics  of  these  plants. 

D.  Examine  and  report  on  any  epiphytes  that  may  be  found. 

References.  Clements,  59  ;  Warming-Groom-Balfour,  57  ;  Pound  and 
Clements,  58. 

158.  Laboratory  study  of  ecological  classes.**  Make  a  sketch  of  at  least 
one  typical  member  of  each  of  the  three  principal  ecological  classes  as  based 
on  water  requirements.  Make  careful  studies  of  any  available  material  and 
discuss  as  many  as  possible  of  the  following  topics  : 

A.  Relative  importance  of  the  root  system  in  aquatic  plants. 

B.  Special  provisions  for  photosynthesis,  respiration,  and  circulation  of 
air  in  the  plant  body  of  aquatic  plants. 

C.  Comparison  of  the  structure  of  the  leaves  of  deciduous  trees,  broad- 
leaved  evergreens  (such  as  holly,  live  oak,  and  some  rhododendrons), 
and  needle-leaved  evergreens.  In  this  study  pay  especial  attention  to 
the  total  area  of  the  three  kinds  of  leaves,  to  their  relative  thickness, 
to  the  thickness  of  the  cuticle  and  the  epidermis,  and  to  the  protection 
of  stomata  by  their  position  at  the  bottom  of  grooves  or  pits  in  the 
epidermis. 

D.  Appearance  of  plants  in  their  resting  condition  (during  winter's  cold 
or  summer's  drought)  in  any  available  bulbous-  or  tuberous-rooted 
species  or  in  fleshy-rooted  biennials  (e.g.  parsnips,  beets,  or  carrots). 

E.  Characteristics  of  plants  slightly,  moderately,  and  decidedly  xero- 
phytic,  as  illustrated  by  wild  plants  of  the  neighborhood  or  (if  these 
are  not  obtainable)  by  such  species  as  Euphorbia  spleiidens,  houseleek, 
Echeveria,  and  cactuses. 

F.  Difference  in  the  appearance  of  a  species  grown  in  dry  soil,  with 
leaves  exposed  to  warm,  dry  air,  and  that  grown  in  damp  soil  under  a 


PLANT  ASSOCIATIONS  177 

bell  glass  (e.g.  young  plants  of  any  xerophytic  grasses,  houseleeks, 
dandelions,  shepherd's  purse,  gorse  i). 
G.  Tolerance  of  salt,  as  determined  by  water  cultures,  in  one  to  six  per 
cent  solutions  of  seedlings  of  ordinary  garden  annuals  and  seedlings 
of  such  halophytes  as  the  salt-marsh  grasses  {Syartiiia  and  others), 
marsh  rosemary  (Statice)^  samphire  {Salicornia),  and  saltwort  (.S'a/.sofa). 
The  plants  which  live  longest  with  the  roots  immersed  in  a  solution  of 
any  given  strength  are  the  most  decidedly  halophytic. 

Kkiehknces.    Kerner-Oliver,  2  ;  Schimper-Fisher,  56 ;  Warming-Groom- 
Balfour,  57  ;  Haberlandt,  33. 


PLANT  ASSOCIATIONS;   ZONATION 

159.  Field  study  of  associations.*  *  ^'isit  any  well-detiiied  associ- 
ations that  are  readily  accessible,  such  as  lake  or  pond,  marsh, 
river  valley  ("  bottom  land  "),  upland  woods,  hill  or  cliff  side,  wet 
prairie,  dry  prairie,  and  other  associations. 

A.  Note  what  are  the  characteristic  plants  of  each  kind  of 
association,  and,  if  necessary,  collect  specimens  of  these  and 
bring  them  to  the  laboratory  to  be  named. 

B.  Make  a  detailed  study  of  at  least  one  association,  noting  all 
that  is  possible  of  the  physical  conditions,  especially  of  mois- 
ture and  light,  the  habits  of  life,  and  mutual  relations  of 
the  plants  which  compose  it.  For  example,  if  the  association 
is  a  wooded  one,  make  lists  of : 

(1)  The  trees,  their  grouping,  relative  height,  relative  density 
of  shade,  comparative  number  of  each  species,  probable 
origin  (e.g.  means  by  which  seeds  were  planted  and  source 
from  which  they  came). 

(2)  The  larger  shrubs. 

(3)  The  undershrubs. 

(4)  Herbaceous  plants. 

(5)  Parasitic  or  saprophytic  seed  plants. 

If  there  is  any  law  to  account  for  the  way  in  which  the 
plants  of  (2),  (3),  and  (4)  are  unequally  distributed  over  the 

1  Ulex. 


178 


ECOLOGY 


forest  floor,  try  to  establish  it,  noting  especially  their  relation 
to  the  relative  moisture  of  the  soil  and  to  light. 
Keferences.    Clements,  59 ;    Principles,  Chapter  XXXVII  ; 
Wa rill ing-Groom-Balf  our,  57  ;   Schimper-Fisher,  56. 


an. 


Fig.  6.    Model  for  grouping  of  drawings  in  type  studies 

base  of  a  plant  of  shepherd's  purse  (Capsella  Bursa-pastoris) ,  x  ^ ;  /•,  the  main 
root ;  B,  upper  part  of  the  inflorescence,  X  1 ;  C,  two  leaves,  —  I  from  the 
upper  part;  II  from  the  base  of  the  plant,  x  1;  D,  a  flower,  x  3;  E,  the 
same,  with  sepals  and  petals  removed,  X  3;  F,  petal;  G,  sepal;  H,  stamen, 
X  10;  /,  filament;  an.,  anther;  /,  a  fruit  with  one  of  the  valves  removed  to 
show  the  seeds,  X  4;  J",  longitudinal  section  of  a  seed,  X  8;  if,  the  embryo 
removed  from  the  seed,  X  8;  Z,  the  first  leaves  (cotyledons) ;  St.,  the  stem  end- 
ing in  the  root ;  L,  cross  section  of  the  stem,  X  20;  fh.,  fibro-vascular  bundle ; 
M,  a  similar  section  of  the  main  root,  x  15 ;  N,  diagram  of  the  flower.  —  After 
Campbell 


160.  Field  study  of  zonation. 

A.   Select   any  locality  where  two 
meet  and  determine  : 
1.  The  characteristic  plants  of  each  association 


more  plant  associations 


TYPE  STUDIES,   SEED   PLANTS  179 

2.  What  })liints  (if  any)  are  coininoii  to  two  or  iiior(!  asso- 
ciations. 

3.  Some  of  the  causes  of  the  boundaries  between  associations, 
and  whether  these  boundaries  are  fixed  or  shifting. 

B.  Make  a  sketch  map  of  the  series  of  zones  on  the  same  gen- 
eral plan  as  that  of  Fig.  366  in  Frinciples,  and  if  possible 
secure  one  or  more  photographs  of  the  series,  with  a  large 
numbered  placard  set  up  in  a  prominent  position  in  each  zone. 

STUDY  OF  TYPES  OF  SEED  PLANTS* 

161.  Family  Pinaceae.i 

162.  Family  Liliaceee.  Any  obtainable  genus  may  be  used  to  represent 
the  family.  Lilies,  tulips,  dogtooth  violets  (Erythronium),  Scilla  sibirira,  or 
Roman  hyacinths  answer  excellently.  Since  it  is  to  be  had  of  florists  during 
the  winter  months  and  in  gardens  for  a  long  time  in  spring,  the  lily  of  the 
valley  {Convallaria)  is  here  taken  as  a  type.  As  an  alternative  the  study  of 
Erythronium  is  also  outlined. 

Convallaria  majalis,  L. 

A.  Sketch  the  entire  plant. 

B.  Does  the  underground  portion  all  belong  to  the  root  system  ?  Give 
reasons  for  conclusion.  Is  it  highly  specialized  for  storage  of  reserve 
material  ? 

1.  Test  a  piece  of  it  (collected  in  winter)  for  starch.  Sec.  12. 

2.  Cut  a  cross  section  of  the  most  vigorous  portion,  examine  with  m.p., 
and  decide  which  of  the  types  of  stem  studied  in  Sees.  25,  26,  it 
most  resembles. 

3.  In  early  spring  note  the  manner  in  which  the  plant  emerges  from 
the  ground. 

C.  In  the  portion  above  ground  note  first  the  scale  leaves,  and,  higher  up, 
the  foliage  leaves.    Label  these  in  your  sketch. 

1.  Are  both  leaf  surfaces  equally  or  unequally  exposed  to  the  light? 
Hold  a  leaf  up  to  the  light  and  study  its  venation.    Describe  it. 

*  To  THE  Instructor:  As  these  studios  consume  much  tiiiio,  it  may  ho  found 
desirable  to  select  only  a  few  of  tliein.  One  of  the  loniicr  oiios,  like  Soc.  l(i.")  or 
Sec.  167,  thorou.i;hly  worked  out,  is  worth  more  than  tlic  whole  series  hurriedly 
done. 

1  A  detailed  study  of  the  pine  may  be  found  in  Sec.  13H.  It  may.  if  necessary, 
be  simplified  to  make  it  homologous  with  those  studies  ol  lamilies  of  angio- 
sperms  which  here  follow  hy  omitting  some  of  the  iiistolojiical  work  and  the 
larger  part  of  the  details  about  the  process  of  reproduction  in  gymnosperms. 


180  KCOLOGY 

2.  Cut  a  cross  section  of  a  leaf,  examine  with  m.p.,  and  sketch  a  por- 
tion extending  from  the  one  epidermis  to  the  other.  Describe  in  a 
few  words  the  characteristics  of  the  leaf  structure  as  compared  with 
any  others  you  have  studied. 

D.  Note  the  mode  of  origin  of  the  peduncle  {scape). 

E.  Note  the  position  of  the  flowers.  Uses  of  this.  Describe  the  flower, 
making  a  diagram  of  a  longitudinal  section  and  a  cross  section. 

F.  If  fruit  of  the  preceding  season  (in  alcohol  or  formalin)  is  at  hand, 
describe  it.    Does  it  reproduce  mainly  by  seed  or  by  other  means  ? 

G.  Does  this  appear  to  be  a  sun  plant  or  a  shade  plant  ?  Reasons  for 
conclusion.  Is  it  a  mesophyte  or  a  xerophyte  ?  What  is  its  habitat  in 
a  wild  state  ?  Look  for  insect  visitors.  What  attractions  has  the  flower 
for  these  ?    Could  it  be  readily  pollinated  without  them  ? 

Erythronium. 

A.  Sketch  the  entire  plant. 

B.  If  possible,  dig  away  the  earth  with  a  trowel  and  make  a  diagram 
to  show  how  the  aerial  parts  stand  above  ground  and  how  the  un- 
derground portion  is  distributed.  Describe  the  bulbs.  Of  what  use 
are  they  ? 

1.  Test  one  for  starch.  Sec.  12. 

2.  Can  they  be  drawn  from  the  ground  by  pulling  the  leaves  and 
scape  ?    Advantage  ?    Has  the  plant  a  stem  ? 

C.  How  do  the  young  leaves  emerge  from  the  ground?  What  is  their 
position  when  full  grown  with  reference  to  light  ?  Strip  off  epidermis 
from  both  surfaces  and  study  with  m.p.    Differences  ?    Explain. 

D.  What  is  the  position  of  the  fully  opened  flower  ?  Advantage  ?  De- 
scribe the  flower. 

1.  Make  a  diagram  of  the  cross  section. 

2.  Make  a  diagram  of  the  longitudinal  section. 

3.  Look  for  nectar  and  nectaries.  What  insect  visitors  frequent  the 
flower  ? 

E.  Do  many  seeds  ripen  ?  Can  the  plant  reproduce  itself  otherwise  than 
by  seed  ? 

F.  Is  the  species  of  Erythronium  studied  a  sun  plant  or  a  shade  plant,  a 
mesophyte  or  a  xerophyte  ?  Do  its  leaves  and  blossoms  mature  earlier 
or  later  than  those  of  the  larger  plants  amid  which  it  grows?  Advan- 
tages?   What  becomes  of  the  leaves  during  the  summer  ? 

Plants  of  the  lily  family  are  readily  distinguished  from  tliose  of  the  near- 
est related  families.  They  differ  from  the  rushes  on  the  one  hand  in  having 
a  well-developed,  not  membranous,  perianth,  and  from  the  members  of  the 
amaryllis  family  and  the  iris  family  on  the  other  by  having  hypogynous 
flowers.    The   Liliacece  are  divided    into    about  ten    subfamilies  of   very 


TYPE    STUDIES,   SEED   PLANTS  181 

unequal  numbeis.  Sninr  of  iho  iiinst  obvious  differences  between  these 
relate  to  the  bulb  or  r()o1s(oci<  or  the  aerial  stem. 

Erythronium  belongs  to  the  lily  subfamily  and  Convallaria  to  the  aspara- 
gus subfamily. 

Give  reasons  why  the  lily,  dogtooth  violet,  tulip,  trillium,  asparagus,  lily 
of  the  valley,  hyacinth,  crown  imperial,  and  onion  should  be  classed  as  of 
the  same  family. 

163.  Family  Ranunculaceae.  Study  any  obtainable  kind  of  buttercup, 
discarding  such  of  the  following  questions  as  do  not  apply  to  the  species 
in  hand. 

Ranunculus  abort Ivus. 

A.  Sketch  the  entire  plant. 

B.  Describe  the  root  system. 

C.  Cut  the  stem  across  and  note  any  peculiarity  of  its  structure. 

D.  Note  the  three  kinds  of  leaves,  —  "  root  leaves  ''  at  the  base  of  the  stem, 
ordinary  leaves,  and  involucral  leaves.  Sketch  one  of  each  kind. 
What  is  the  advantage  of  having  the  upper  leaves  parted  into  narrow 
divisions  '?  of  having  the  root  leaves  long-petioled  ? 

E.  Describe  the  floral  organs. 

1.  Make  a  diagram  of  a  longitudinal  section  of  the  flower.    How  much 
apparent  union  of  parts  of  the  same  or  of  different  circles  is  there  ? 

2.  Do  all  the  anthers  mature  together  ?    Advantages? 

3.  Do  the  stigmas  and  anthers  mature  together  ?    Advantage  ? 

4.  Look  for  the  nectar  and  nectar  glands.    What  insect  visitors  occur  ? 
Are  the  flowers  self -pollinated  ? 

F.  Study  a  head  of  mature  akenes  and  describe  it.  Does  seed  mature 
abundantly  ?  Why  cannot  this  species  become  a  troublesome  weed 
like  R.  bulbosus  or  R.  acris  ? 

G.  Test  the  flavor  of  any  species  of  Ranunculus  that  you  can  get,  by 
biting  the  fresh  stem.  Explain  uses.  Does  this  buttercup  seem  to 
be  a  more  or  less  highly  specialized  plant  than  the  columbine  (Aqui- 
legla)  or  the  larkspur  {Delphinium)  oi  the  same  family  ?  In  what 
respects  ? 

164.  Family  Rosaceae.  Study  any  kind  of  rose  except  the  cultivatt-d 
varieties  with  double  flowers,  or  any  kind  of  cherry  or  plum. 

Rosa  humilis. 

A.  Describe  the  height  and  mode  of  branching  of  this  rose.  Are  all 
specimens  equally  prickly  ?    Where  do  prickles  occur  '.' 

B.  Sketch  a  typical  leaf  (of  five  leaflets).  How  and  how  much  do  the  leaves 
vaiy?  Study  a  cross  section  of  a  leaf  with  m.p.  to  find  out  how 
much  the  epidermis  protects  against  excessive  transiiiration.  If  con- 
venient, compare  with  a  greenhouse  species,  e.g.  tea  rose. 


182  ECOLOGY 

C.  Describe  the  occurrence  of  the  flower  buds.  When  and  for  how  long 
do  the  flowers  open  ?  Advantage  ?  Look  for  insect  visitors.  What  do 
these  collect  ?  Are  roses  probably  dependent  on  insect  pollination  ? 
Make  a  diagram  of  a  longitudinal  and  of  a  cross  section  of  the  flower. 

D.  Study  fruit  of  the  rose  from  material  in  alcohol  or  formalin.  Are 
fresh  rose  hips  edible  ?  Are  the  seeds  ?  How  long  do  rose  hips  remain 
on  the  branches  ?  Advantage  ?  Have  you  seen  birds  eating  them  ?  At 
what  season  ?  What  becomes  of  the  seeds  when  birds  eat  the  pulp  of 
the  fruit  ?    Are  most  rosebushes  browsed  by  cattle  ?    Reasons  ? 

E.  Is  this  rose  adapted  to  a  moist  or  a  dry  habitat  ?    How  ? 
Prunus  serotina,  wild  black  cherry. 

A.  What  is  the  shape  of  full-grown  trees  ?  Size  of  the  largest  ones  in 
your  vicinity  ? 

B.  Sketch  and  describe  the  leaves. 

C.  Sketch  a  flower  cluster.  Do  cherry  and  plum  trees  blossom  before  or 
after  the  leaves  develop  ?  Are  they  all  alike  in  this  ?  Advantages  of 
blossoming  first  ? 

1.  Make  a  diagram  of  a  longitudinal  and  a  transverse  section  of  the 
flower.    How  many  ovules  are  there  ?    Do  all  mature  ? 

2.  Look  for  nectar  and  nectaries.    Do  the  anthers  all  mature  together  ? 
Are  there  insect  visitors  ? 

D.  Is  the  fruit  edible  ?  Do  birds  gather  it  ?  What  evidence  is  there  of 
wide  distribution  of  the  seeds  ?  Why  do  cherry  trees  often  grow  beside 
fences  ? 

The  rose  family  (as  found  in  temperate  regions)  is  divided  into  four  sub- 
families,—  Spiroeoidece,  Pomoideos,  Rosoideoe,  and  PrunoidecB.  Familiar  rep- 
resentatives of  these  are  the  Spiraea,  the  apple,  the  rose,  and  the  cherry. 
The  most  obvious  differences  between  these  subfamilies  depend  on  the 
development  of  the  receptacle  and  the  way  in  which  the  carpels  are  borne 
on  or  within  it.  In  the  Spiroeoideoe  the  receptacle  is  flattish  and  the  carpels 
are  borne  on  its  surface.  In  the  PomoidecB  the  flowers  are  epigynous  and 
the  carpels  appear  to  be  grown  fast  to  the  hollow  inner  wall  of  the  recep- 
tacle. In  the  Rosoideoe  the  carpels  are  in  some  genera  (as  in  the  rose)  mod- 
erately attached  to  the  ijiterior  of  a  hollow  receptacle,  and  in  other  genera 
(as  in  the  raspberry,  the  blackberry,  and  the  strawberry)  they  are  borne  on 
the  outside  of  a  more  or  less  elongated  and  thickened  receptacle.  In  the 
PomoidecB  there  is  often  but  one  carpel,  which  ripens  only  a  single  seed, 
inclosed  in  a  fleshy  stone  fruit. 

Is  there  any  general  similarity  in  the  size,  habit,  and  degree  of  woodiness 
of  rosaceous  plants  ? 

How  could  all  rosaceous  plants  be  roughly  classified  as  regards  their 
leaves  ? 


TYPE  STUDIES,   SEED   PLANTS  183 

What  can  you  say  of  the  econouiic  iinportaiicc  of  the  family?  Make 
a  list  of  all  the  cultivated  Rosacem  that  you  know  and  state  for  what  each 
is  valued.    Uses  of  some  wild  species  ? 

165.  Family  Leguminosae.  The  black  locust  (Iiobiuia  Pseudo- Acacia) ^  one 
of  the  vetches  {Vicia  or  Lathyrus),  or  the  common  pea  (Pisum)  are  good 
types  for  study. 

Rohmia  Pfteiido-Acacia. 

A.  Sketch  a  well-grown  tree  (best  before  the  leaves  appear). 

B.  Examine  the  roots  for  tubercles.  In  the  locust,  as  in  the  LegiuninoscB 
generally,  these  serve  an  important  purpose  in  manufacturing  soluble 
nitrogen  compounds  for  the  use  of  the  plant. 

C.  Sketch  a  twig  to  show  the  arrangement  of  the  thorns. 

1.  What  are  the  thorns  ?    How  related  to  the  winter  buds  ?    Why  ? 

2.  Are  the  twigs  mature  and  alive  to  their  tips?  How  is  the  growth  of 
the  twig  continued  in  the  spring  ?  What  other  trees  or  shrubs  do 
you  know  with  the  same  characteristics  ? 

8.  Cut  off  a  large  branch  of  locust.  Is  there  much  distinction  between 
sapwood  and  heartwood  ?  For  what  is  the  wood  most  valuable  ? 
What  other  woods  are  notable  in  the  same  way  ? 

D.  Sketch  a  locust  leaf. 

1.  Is  the  number  of  leaflets  constant  ? 

2.  Study  and  report  on  the  positions  of  leaves  on  horizontal  and  vertical 
twigs.    Explain. 

3.  Study  the  leaflet  position  :  (a)  on  outer  branches  in  sunlight ;  {b)  on 
inner  branches  or  in  dull  weather  ;  (c)  at  night. 

4.  Sketch  a  leafy  twig  as  seen  in  positions  of  {a),  {b),  and  (c).  Explain 
the  use  of  each  position. 

Try  to  ascertain  by  studies  of  the  leaves  on  the  tree  what 
percentage  of  the  noon  illumination  on  a  perfectly  sunny  day  is 
necessary  to  produce  position  (a)  and  what  to  produce  posi- 
tion (&).  (For  method  of  measuring  relative  intensities  of  illumina- 
tion see  Exp.  XXVIII.) 

E.  Note  the  time  of  appearance  of  the  flowers  relatively  to  that  of  the 
leaves.  Is  it  the  same  in  all  individuals  ?  In  southern  Italy  the 
flowers  usually  appear  before  the  leaves.    Advantage  of  this  ? 

1.  Sketch  a  twig  with  a  flower  cluster  in  its  natural  position. 

2.  Sketch  an  entire  flower  and  another  dissected.  Why  is  a  flower  of 
this  shape  called  papilionaceous  ? 

3.  Make  a  diagram  of  the  longitudinal  section. 

4.  Make  a  detailed  drawing  of  the  longitudinal  section  of  a  large  flower 
bud,  two  to  four  times  natural  size.  Show  plainly  the  beard  of 
hairs  below  the  stigma. 


184  ECOLOGY 

5.  Remove  from  a  just-opened  flower  all  the  floral  organs  except  the 
pistil  and  make  an  enlarged  drawing  of  the  pistil,  side  view.  Where 
is  pollen  accumulated  on  it  ? 

6.  Which  matures  earlier,  stigma  or  anthers  ? 

7.  Watch  a  bee  visiting  the  flowers  and  note  what  happens  when  she 
alights  on  the  wings.  Why  are  the  wings  and  keel  fastened  together  ? 
Imitate  the  action  of  the  bee  by  pressing  the  wings  and  keel  down- 
ward.   Explain  why  cross  pollination  is  almost  sure  to  occur. 

8.  Make  a  list  of  all  the  attractions  which  this  flower  has  for  insects. 
What  insect  visitors  have  you  observed  ? 

F.  Study  the  ripe  fruit  of  the  locust.  What  becomes  of  it  in  the  autumn  ? 
Are  the  seeds  likely  to  be  destroyed  by  animals  ?  Reasons  ?  Part  of 
the  locust  seeds  of  each  season  grow  within  a  year,  but  others  do  not 
grow  until  succeeding  years.    Advantage  of  this  ? 

G.  Write  a  brief  essay  on  the  ecology  of  the  locust,  explaining  all  its  adap- 
tations with  reference  to  utilizing  bacterial  symbionts,  to  light  supply,  to 
browsing  animals,  to  pollinating  insects,  and  to  reproduction  by  seeds. 

Lathyrus  odoratus,  sweet  pea. 

A.  Sketch  the  entire  plant.  Study  the  distribution  of  the  hairs  on  its 
surface.  Of  what  use  may  these  be  ?  In  southern  Europe,  where  this 
plant  is  common  in  a  wild  state,  snails  are  among  the  most  important 
enemies  of  vegetation  and  they  rarely  attack  hairy  plants. 

B.  Examine  the  roots  for  tubercles.  What  kind  of  a  climber  is  it  ?  How 
does  it  climb  ?    Why  ? 

C.  Sketch  several  leaves  with  tendrils  in  various  stages  of  development. 
How  does  the  tendril  pull  the  plant  toward  any  support  on  which  it 
fastens  ? 

D.  Sketch  a  bit  of  stem  with  a  flower  cluster  in  its  natural  position. 
Make  a  detailed  study  of  the  flower  as  described  under  Robinia. 

E.  Study  the  ripe  fruit  of  the  sweet  pea.  Are  the  pods  likely  to  be  eaten 
by  animals?  Reasons?  Can  you  find  out  how  the  seeds  are  distributed  ? 
Explain  how  the  vetches  are  equipped  to  hold  their  own  as  dwellers  in 
thickets  and  in  tall  grass  or  among  other  large  herbaceous  plants. 

The  family  LeguminoscE  is  a  very  large  and  important  one,  divided  into 
three  subfamilies  —  Mimosoideoe,  CcBsalpinioideoB,  and  PapilionatcB  —  whose 
characteristics  are  based  on  the  structure  of  the  flowers.  The  first,  the  Aca- 
cia subfamily,  is  mostly  tropical ;  the  second,  the  Cassia  subfamily,  contains 
three  quite  familiar  North  American  genera,  —  Cassia  or  wild  senna,  Cercis 
or  redbud,  and  Gleditsia  or  honey  locust.  Most  of  our  familiar  Legu- 
minosoe,  however,  belong  to  the  third  subfamily,  Papilionatoe,  readily  recog- 
nizable by  their  papilionaceous  flowers.  Make  out  a  list  of  those  which  you 
know  are  useful  or  ornamental  and  give  their  uses. 


TYPE  STUDIES,  SEED  PLANTS  185 

166.  Family  Violaces.    Study  any  species  of  violet ;  if  some  of  the  points 
suggested  in  the  following  outline  do  not  fit  the  species  in  hand,  omit  them. 
Viola  palmata. 

A.  Sketch  the  entire  plant. 

B.  Has  it  any  stem  ?    Explain. 

C.  Sketch  one  of  the  first  leaves  of  the  season  and  a  later  one. 

D.  Sketch  a  flower  in  profile  in  its  natural  position. 

1.  What  kind  of  symmetry  has  it?  Does  the  flower,  seen  from  in 
front,  appear  open  or  closed  ?  How  much  of  the  stamens  and  pistils 
can  be  seen  ? 

2.  Make  a  diagram  of  the  cross  section  of  the  flower. 

3.  Remove  the  petals.  Is  the  spur  a  part  of  the  calyx  or  the  corolla  ? 
It  serves  as  a  nectary. 

4.  Note  the  two  nectar  glands  which  project  from  stamens  into 
the  spur. 

5.  Make  a  sketch  of  the  magnified  pistil,  surrounded  by  the  stamens. 

6.  Are  the  filaments  united  ?  the  anthers  ?  Do  the  anthers  discharge 
inwardly  or  outwardly  ?    Is  the  pollen  dry  or  sticky  ? 

7.  Note  that  the  pollen  when  shed  collects  in  a  sort  of  cone  formed  by 
the  united  anthers,  which  is  closed  at  the  narrow  end  by  the  pistil. 
When  a  visiting  insect,  as  a  bee  seeking  nectar,  thrusts  its  tongue 
into  the  small  end  of  the  cone,  what  would  become  of  any  pollen 
which  the  insect  brought  with  it  ?  Would  other  pollen  be  carried 
away  ?    Result  ? 

8.  Thrust  a  slender,  moistened  toothpick  gently  into  the  opening  of  the 
corolla,  and  after  withdrawing  examine  it  with  a  lens.    Result  ? 

9.  What  means  have  violets  of  advertising  their  supply  of  nectar  ? 
Compare  the  attractiveness  of  several  species. 

10.  Look  for  insect  visitors.  Do  they  all  explore  the  interior  of  the 
flower,  as  shown  in  Principles,  Fig.  325  ? 

11.  Many  violets  form  most  of  their  seed  from  apetalous  cleistogamous 
flowers  (see  Principles,  Sec.  408).  Is  Viola  pabnata  one  of  these  ? 
Study  specimens  in  late  summer  or  early  fall  to  determine  this  point. 
What  are  some  advantages  of  cleistogamy  ?  disadvantages  ?  How 
would  a  plant  with  some  insect-pollinated  flowers  and  other  cleistog- 
amous ones  avoid  the  disadvantages  mentioned  ? 

E.  What  mechanism  have  the  capsules  for  distributing  seeds  ? 

F.  Are  any  violets  moderate  xerophytes  ?    Are  any  hydrophytes  ?    Does 
the  species  studied  belong  to  either  class  ? 

The  Violacece  constitute  a  small  and  unimportant  family,  but  the  flowers 
are  decidedly  interesting  from  the  perfection  of  their  adaptation  for  chkss 
and  self  pollination. 


186  ECOLOGY 

167.  Family  Compositae.  Most  of  the  genera  of  this  family  found  in 
the  United  States  are  summer  or  autumn  flowering.  Two  common  genera 
which  flower  in  spring  are  Taraxacum  and  Erigeron. 

Taraxacum  officinale,  common  dandelion. 

A.  Sketch  the  entire  plant. 

1.  Notice  the  rosette  formed  by  the  leaves,  all  borne  close  to  the 
ground  or  even  pulled  below  the  surface  by  contraction  of  the  tap 
root.  What  is  the  use  of  this  shortening  of  the  tap  root  ?  What 
other  plants  show  it  ? 

2.  Sketch  the  plant  as  seen  from  above.  How  much  do  the  leaves 
overlap  and  shade  each  other  ?  How  much  do  they  interfere  with 
the  growth  of  grass  in  a  lawn  ?   Advantages  ? 

3.  Taste  the  root  and  leaves.  Use  of  this  taste  ?  Are  the  leaves  easily 
injured  by  frost  ? 

B.  1.  Sketch  the  slender  scape  with  its  head  of  flowers.    How  do  you 

know  that  the  whole  yellow  "  dandelion  "  is  an  inflorescence  and 
not  a  flower  ?    Advantage  of  grouping  flowers  in  a  head  ? 

2.  Changes  in  length  of  scape  as  it  grows  older  ?    Advantages  ? 

3.  Describe  the  involucre. 

4.  What  is  its  condition  in  the  bud  ?  in  a  fully  opened  head  ?  in  a 
head  that  is  past  blooming ?  in  a  head  when  the  fruits  (  "seeds "  ) 
are  beginning  to  disperse  ? 

5.  Of  what  use  is  the  involucre  ? 

6.  Make  a  longitudinal  section  through  a  newly  blooming  head  and 
note  whether  all  the  flowers  mature  together. 

7.  The  cushion-like  expanded  extremity  of  the  scape,  from  which  the 
flowers  spring,  is  a  common  receptacle  for  all  the  flowers  of  the  head. 

C.  1.  Note    and   describe    the   change    in   form  of   the   corolla   as   the 

buds  open. 

2.  Decide  from  the  number  of  teeth  at  the  tip  of  the  corolla  and  the 
number  of  stamens  what  is  the  numerical  plan  of  the  flower. 

3.  Slit  open  the  corolla  of  a  bud  with  a  needle  and  scalpel,  or  two 
needles,  under  the  magnifying  glass,  and  note  the  structure  of  the 
flower.  How  many  stamens  are  there  ?  From  what  part  of  the 
flower  do  the  filaments  spring  ?  Are  the  anthers  attached  to  each 
other  ?  How  do  they  open  ?  Position  of  the  anthers  relative  to  the 
style  *?  How  many  branches  has  the  stigma  ?  What  is  their  form 
and  position  (a)  in  the  bud  ?  (6)  in  the  newly  opened  flower  ? 
(c)  in  the  flower  just  before  withering  ?  What  portion  of  the  stigmas 
is  hairy  ? 

4.  When  the  stigmas  emerge  from  among  the  anthers  what  do  they 
bring  with  them  ?   Importance  of  this  ?   Could  the  movements  of 


TYPE   STUDIES,   SEED   PLANTS  187 

the  stigmas  cause  self-pollination  ?   At  what  period  in  their  devolo].- 
ment  ?  Advantages  of  this  ? 

5.  Look  for  nectar.  How  high  does  it  rise  in  the  corolla  tube  ?  Acces- 
sibility to  small  insects  ? 

6.  How  many  kinds  of  insect  visitors  do  you  find  ?  i 

7.  Is  the  head  open  on  sunny  and  cloudy  days  alike  ?  Is  it  open  all 
night  ?  Advantages  ?  Mark  a  head  by  tying  twine  loosely  about  the 
scape  and  note  how  long  it  remains  in  blossom,  how  long  it  remains 
closed  after  blossoming,  and  how  long  after  reopening  the  last  fruits 
are  dispersed. 

D.  Sketch  a  fruit  somewhat  magnified  and  label  the  parts.  Test  the 
traveling  powers  of  some  akenes  in  a  gentle  breeze. 

E.  Study  the  distribution  of  dandelion  plants  in  your  neighborhood,  state 
where  they  thrive  best,  and  give  reasons. 

F.  Write  a  brief  essay  on  the  ecology  of  the  dandelion,  discussing  : 

(1)  Relations  to  other  plants. 

(2)  Relations  to  leaf-eating  insects  and  grazing  animals. 

(3)  Relations  to  pollinating  insects. 

(4)  Relations  to  weather. 

(5)  Distribution  of  seed. 

Erigeron  philadelphicus,  common  fleabane  (or  other  species). 

A.  Study  the  fully  opened  heads  and  make  out  a  list  of  resemblances 
to  and  differences  from  the  head  of  the  dandelion.  Note  that  every 
flower  in  the  dandelion  head  has  a  strap-shaped  corolla,  and  is  bisexual. 

1.  Where  are  strap-shaped  flowers  of  the  fleabane  ?    Are  they  bisexual? 

2.  Sketch  under  the  lens  a  tubular  flower. 

B.  Look  for  insect  visitors. 

C.  Discuss  the  relative  equipment  of  the  dandelion  and  the  fleabane  for 
success  in  life. 

The  family  ComposltcB  is  the  largest  family  of  seed  plants,  comprising 
about  eleven  thousand  species.  It  is  usually  considered  to  be  the  highest 
family.  Not  many  Conipositce  in  temperate  climates  are  shrubby  or  tree^ 
like,  but  as  herbs  they  show  the  greatest  diversity  of  form  and  ecological 
characteristics.  As  a  rule,  they  are  extremely  successful  in  maturing  and 
distributing  seed,  and  for  this  and  other  reasons  constitute  very  formi- 
dable weeds. 

Make  a  list  of  some  of  the  commonest  weeds  of  this  family  in  your 
neighborhood. 

References.  Principles,  Chapters  XXXII,  XXXIII  ;  Strasburger,  Noll, 
Schenck,  Karsten,  1  ;  Warming-Mobius,  37  ;  Engler,  30 ;  Knuth- 
Davis,  62  ;  Kerner-Oliver,  2. 

1  Nearly  a  hundred  species  have  been  noted  in  a  single  locality. 


BOTANICAL  MICROTECHNIQUE 


168.  Introduction.  This  section  will  describe  the  technique  of  a  number  of 
well-known  histological  and  cytological  methods  involving  the  preparation 
of  material.  Its  object  is  to  present  simple  and  clear  descriptions  of  tried 
methods  that  can  be  depended  upon  to  give  good  results.  Detailed  treatments 
may  be  found  in  a  number  of  treatises.  ^  The  best  general  accounts  of  his- 
tological methods  in  English  are  those  in  Strasburger-Hillhouse,  6,  which  is 
based  on  Strasburger's  Das  hotanische  Praktikum.  The  subject-matter  of  the 
following  brief  account  will  be  taken  up  under  the  following  headings  : 

General  reagents  employed  in  temporary  preparations. 

Some  special  reagents  for  microchemical  and  other  tests  and  temporary 
preparations. 

Killing  and  fixing. 

The  preservation  of  material. 

General  staining  methods. 

Mounting  in  balsam  and  glycerin. 

Imbedding  in  paraffin. 

Sectioning. 

Staining  on  the  slide. 


GENERAL  REAGENTS  EMPLOYED  IN  TEMPORARY 
PREPARATIONS 

169.  General  reagents  employed  in  temporary  preparations. 

A.  Iodine  solutions.  Dissolve  5  grams  potassium  iodide  in  100  cc.  distilled 
water,  and  add  1  gram  of  iodine.  This  gives  a  good  strength  for  most 
purposes.  It  may  be  diluted  if  desired,  and  should  be  used  of  half  this 
strength,  or  weaker,  when  the  color  of  the  solution  might  interfere  with 
the  clearness  of  vision,  as  when  zoospores  are  stained  to  show  their  cilia. 
Iodine  solutions  kill  protoplasm  quickly,  staining  it  a  deep  brown, 
especially  the  nucleus  and  chromatophores.    They  furnish  the  simplest 

1  Zimmermann-Humphrev,  Botanical  Microtechnique.  Henry  Holt  &  Co., 
New  York,  1893.  Poulsen-Trelease,  Botanical  Micro-Chemistry,  S.  E.  Cassino 
&  Co.,  Boston,  1884.  Chamberlain,  Methods  in  Plant  Histology,  The  University 
of  Chicago  Press,  Chicago,  1905. 

188 


GENERAL   REAGENTS  189 

tests  for  starch  (Sec.  12),  coloring  the  grains  blue,  or  a  deep  brown  if  the 
solution  be  too  strong.  Cellulo.se  (Sec.  12)  is  generally  stained  yellow 
or  brown,  which  changes  to  blue  if  a  strong  solution  of  sulphuric  acid 
be  applied  after  the  iodine. 

B.  Chlorzinc  iodine.  This  is  a  troublesome  reagent  to  prepare,  but  the  best 
test  for  cellulose.  Dissolve  zinc  in  pure  hydrochloric  acid  and  evapo- 
rate the  solution  (with  metallic  zinc  present  in  it  during  the  pr()ces.s)  to 
the  density  of  sulphuric  acid.  Add  as  much  potassium  iodide  as  the 
solution  will  dissolve,  and  finally  as  much  metallic  iodine  as  it  will 
take  up.  The  solution  will  keep  better  away  from  the  light.  Chlorzinc 
iodine  stains  pure  cellulose  a  clear  blue  or  violet.  It  reacts  best  on 
preparations  in  water. 

C.  Potash  solution.  A  6%  solution  of  potassium  hydrate,  or  caustic  potash, 
in  water  is  an  excellent  clearing  and  softening  agent.  A  15';  solution 
is  necessary  for  some  subjects,  as  firm  leaf  sections.  The  potash 
solution  may  be  neutralized  by  washing  the  sections  in  commercial 
acetic  acid  and  then  mounting  them  in  the  latter. 

Potash  solutions  must  be  kept  tightly  stoppered.  Rubber  stoppers 
answer  well;  glass  ones  should  be  covered  with  paraffin,  otherwise 
they  are  likely  shortly  to  become  stuck  beyond  the  power  of  removal. 

D.  Acetic  acid.  A  1%  solution  of  glacial  acetic  acid  in  water  will  fix  and 
frequently  bring  out  clearly  the  nucleus  and  other  protoplasmic  struc- 
tures of  a  cell.  Beautiful  temporary  preparations  may  then  be  made 
by  staining  with  gentian  violet  (see  F)  or  methyl  green  (Sec.  186,  B). 

E.  Eosin.  A  strong  solution  of  eosin  in  water  is  the  most  useful.  Alco- 
holic solutions  may  be  employed  when  the  preparation  is  in  alcohol. 
This  stain  has  the  peculiar  advantage  of  coloring  protoplasm  alone, 
leaving  the  cell  wall  unaffected. 

F.  Gentian  violet.  A  deep  violet  solution  in  1%  acetic  acid  is  a  good 
strength  for  temporary  staining  of  fresh  material,  or  after  fixing  with 
1%  acetic  acid  (see  D). 

G.  Alcohol.  Alcohol  has  its  chief  value  for  temporary  preparations  in 
driving  out  air  bubbles  from  material  which  will  not  wet  easily  in 
water,  as,  for  example,  the  mycelium  of  fungi. 

H.  Distilled  water.  Temporary  preparations  of  living  plants  are  mounted 
in  tap  water,  or  that  in  which  they  live,  if  aquatic.  Distilled  water  is 
used  when  the  preparations  are  made  from  preserved  material. 

I.  Glycerin.  A  solution  one  third  glycerin  and  two  thirds  distilled  water 
is  very  useful  in  preserving  temporary  preparations.  A  drop  or  two 
placed  at  the  edge  of  the  cover  glass  will  prevent  the  preparation  from 
drying  up.  This  .solution,  or  one  considerably  stronger,  is  also  used 
for  permanent  preparations  when  inclosed  in  a  cement  ring  (Sec.  188). 


190  BOTANICAL  MICROTECHNIQUE 

SOME  SPECIAL  REAGENTS  FOR  MICROCHEMICAL 
TESTS  AND  TEMPORARY  PREPARATIONS 

170.  Some  special  reagents  for  microchemical  tests  and  temporary  preparations . 

A.  Alkanet  root  tincture.  Add  enough  bits  of  alkanet  root  to  95%  alcohol 
to  color  it  deep  red.  The  solution  serves  as  a  test  for  oils  and  resins 
(Sec.  12),  coloring  them  red. 

B.  Ammonia.  Ordinary  commercial  ammonia  water  is  used  after  treat- 
ment of  sections,  etc.,  with  nitric  acid  to  give  the  xanthoproteic 
reaction  (Sec.  12),  coloring  proteids  yellow  or  orange. 

C.  Chloral  hydrate.  A  solution  of  eight  parts  of  chloral  hydrate  in  five  parts 
of  water  by  weight  forms  an  excellent  clearing  reagent  for  growing 
points  and  pollen  grains. 

D.  Chloroform.  Removes  oil  from  sections  of  seeds  which  are  to  be 
examined  for  aleurone  grains. 

E.  Fehling^s  solution.  This  reagent  may  be  bought  of  dealers  in  chemicals. 
It  is  usually  made  up  in  the  form  of  two  or  three  solutions,  which 
are  to  be  mixed  only  at  the  time  of  using.  The  following  formula  is 
convenient,  and  keeps  well  in  a  cool  place.  Dissolve  34.64  grams  pure 
crystallized  copper  sulphate  in  200  cc.  of  distilled  water.  Mix  the  solu- 
tion with  150  grams  of  neutral  potassium  tartrate  dissolved  in  about 
500  cc.  of  a  ten  per  cent  solution  of  sodium  hydrate.  The  whole  is 
then  to  be  diluted  with  water  to  1  liter,  and  100  cc.  of  glycerin  added. 
The  solution  serves  as  a  test  for  sugar  (Sec.  12). 

F.  Millon's  reagent.  Dissolve  metafllic  mercury  in  its  own  weight  of  c.p. 
concentrated  nitric  acid  and  dilute  the  solution  with  its  own  volume  of 
distilled  water.  This  reagent  swells  cell  walls  and  usually  colors  pro- 
teids (Sec.  12)  a  characteristic  brick  red. 

G.  Nitric  acid.  C.p.  nitric  acid,  slightly  or  not  at  all  diluted,  is  used  as 
a  test  for  proteids  (Sec.  12).  It  is  also  used  in  Schultze's  macerating 
mixture  (see  M). 

H.  Olive  oil.  This  is  used  as  a  mounting  fluid  for  sections  of  seeds  with 
aleurone  grains. 

I.  Phloroglucin.  1-5%  solutions  in  water  or  alcohol  are  used  as  a  test  for 
lignified  tissue  (Sec,  12). 

J.  Potassium  chlorate.  This  is  used  as  an  ingredient  of  Schultze's  macer- 
ating mixture  (see  M). 

K.  Potassium  permanganate.  A  4%  solution  of  this  compound  in  water  is 
used  as  a  stain  to  distinguish  roots  from  stems  in  very  young  seedlings. 

L.  Safranln.  A  saturated  or  sometimes  a  half-saturated  aqueous  solution 
of  this  stain  is  valuable  for  differentiating  tissue  elements,  e.g.  in  stem 


SPECIAL  REAGENTS  191 

sections  or  leaf  sections.    There  are  several  good  forniuhe  for  safranin 
stains  (Sec.  184). 

M.  Schultze's  macerating  mixture.  This  mixture  is  used  to  disintegrate 
tissues  (e.g.  wood)  to  obtain  individual  cells.  The  material  to  be  treated 
should  be  in  small  bits  cut  lengthwise.  Place  the  sections  in  a  test 
tube  and  pour  on  just  enough  strong  nitric  acid  to  cover  the  material. 
Add  a  few  crystals  of  potassium  chlorate  and  heat  gently  until  bubbles 
are  given  off  and  the  substance  treated  becomes  white.  If  violent 
action  occurs  and  abundant  reddish  fumes  are  evolved,  repeat  the 
operation  with  fresh  bits  of  the  substance  to  be  macerated,  using  less 
chlorate.  The  process  must  be  conducted  out  of  doors  or  under  a  hood, 
as  the  acid  vapors  produced  are  very  corrosive  and  injure  microscopes 
and  most  metallic  apparatus.  When  the  maceration  is  finished  the 
fibrous  material  left  should  be  thoroughly  rinsed  with  successive  por- 
tions of  water  until  all  traces  of  acid  are  removed.  It  may  then  be 
teased  apart  with  needles  and  preserved  in  glycerin,  and  portions 
mounted  for  examination  as  required. 

N.  Sugar.  Cane  sugar  is  used  in  the  preparation  of  solutions  for  the 
culture  of  pollen  tubes  (Experiment  XLII),  alga  (Sec.  200),  and  germi- 
nating spores  of  mosses  and  ferns  (App.  19  and  App.  20). 

Solutions  of  the  required  strengths  can  be  made  by  weighing  out 
the  necessary  amounts  of  granulated  sugar  and  adding  to  measured  or 
weighed  amounts  of  tap  water.  One  and  a  half  per  cent  of  gelatin 
may,  with  advantage,  be  added  to  most  of  the  solutions  for  the  culture 
of  pollen  tubes. 

KILLING  AND  FIXING 

171,  The  principles  of  kiUing  and  fixing.  Fixing  is  the  preservation  of  the 
structure  of  protoplasm  immediately  after  death  as  nearly  as  possible  like 
that  of  the  living  cell.  Killing  and  fixing  are  generally  accomplished  by  the 
same  fluid.  Fixing  agents  have  in  their  composition  elements  (as  chromium, 
osmium,  platinum,  etc.)  which  living  protoplasm  normally  never  or  but 
rarely  encounters,  or  severe  combinations  of  poisons  that  are  utterly  foreign 
to  it.  The  ability  of  a  killing  fluid  to  fix  undoubtedly  rests  on  its  power 
to  subject  protoplasm  to  a  shock  so  sudden  and  great  that  there  is  little  or 
no  time  for  great  structural  changes  to  take  place,  while  the  reagent  itself 
must  not  cause  disorganization.  Fixed  material  nmst  later  be  preserved,  a 
process  involving  quite  different  methods  and  reagents  (Sees.  177,  178). 

172.  Chrom-acetic  acid.  The  combination  of  chromic  and  acetic  acids  in 
various  proportions  has  proved  to  be  a  very  satisfactory  general  fixing  agent, 
and  is  among  the  cheapest.    Three  grades  of  chrom-acetic  acid  will  be  found 


192  BOTANICAL  MICROTECHNIQUE 

useful,  — a  weak,  a  medium,  and  a  strong.  Any  shrinkage  of  the  cell  con- 
tents during  fixation  indicates  that  the  solution  is  too  strong  in  chromic 
acid,  which  has  a  tendency  to  contract  the  protoplast,  partially  compen- 
sated by  the  acetic  acid  which  is  employed  because  of  its  tendency  to  swell 
the  cell  contents. 

A.  Weak  chrom-acetic  acid  ^ : 

1%  chromic  acid        25  cc.  making  .25%  chromic  acid. 
1%  acetic  acid  10  cc.  making  .1%  acetic  acid, 

distilled  water  65  cc. 

100  cc. 
This  is  generally  the  most  satisfactory  strength  of  chrom-acetic  acid 
for  algse  and  fungi,  and  the  more  delicate  structures  of  the  liverworts 
and  mosses  will  be  excellently  fixed  by  it,  likewise  fern  prothallia. 

B.  Medium  chrom-acetic  acid  : 

1%  chromic  acid      70  cc.  making  approximately  .7%  chromic  acid, 
glacial  acetic  acid        .5  cc.  making  approximately  .5%  acetic  acid, 
distilled  water         30  cc. 
100.5  cc. 
A  good  fluid  for  most  work  on  the  histology  of  the  pteridophytes 
and  seed  plants  and  the  firmer  structures  of  mosses  and  liverworts. 

C.  Strong  chrom-acetic  acid : 

1%  chromic  acid  100  cc.  making  approximately  1%  chromic  acid. 

glacial  acetic  acid         1  cc.  making  approximately  1%  acetic  acid. 

ToTcc. 
This  solution  may  prove  more  satisfactory  than  medium  chrom-acetic 
acid  when  the  tissue  is  dense  or  with  very  heavy  cell  walls. 
The  determinations  of  the  proper  relative  strengths  of  chromic  and  acetic 
acids  become  matters  of  experience  and  experiment  which  must  be  tested 
with  untried  subjects,  but  those  who  use  this  fixing  fluid  are  soon  able  to 
judge  very  accurately  the  strength  and  time  necessary  for  good  results. 
Chrom-acetic  acid  keeps  perfectly,  and  costs  so  little  that  it  may  be  made  up 
in  large  quantities ;  it  is  the  most  useful  general  fixing  agent  in  the  labo- 
ratory.   It  should  be  employed  in  liberal  quantities,  perhaps  one  hundred 
times  the  bulk  of  the  material,  or  in  such  amounts  that  the  fluid  is  not 
noticeably  discolored  by  the  material. 

1  The  formulae  in  this  account  are  generally  given  in  terms  of  100  cc.  The 
proportions  may  be  multiplied  by  tens  and  hundreds  for  larger  quantities. 
Chrom-acetic  acid  is  so  useful  a  reagent  that  a  laboratory  should  always  have  a 
stock  supply.  Another  plan  is  to  keep  on  the  same  shelf  or  table  a  large  bottle  of 
1%  chromic  acid,  another  of  1%  acetic  acid,  and  a  small  bottle  of  glacial  acetic 
acid,  together  with  a  large  and  small  graduate  and  the  formulae  posted  on  the 
wall.    Solutions  may  then  be  made  up  at  any  moment. 


KILLING  AND   FIXING  193 

Material  is  generally  left  in  chrom-acetic  acid  for  twelve  hours  or  more, 
but  very  delicate  structures  require  only  an  hour  or  two.  Some  algge  with 
soft  cell  walls,  such  as  Polysiphonia,  will  go  all  to  pieces  if  left  in  the  weak 
formula  more  than  five  or  ten  minutes.  Solutions  employed  upon  the  marine 
algae  must  be  made  up  in  salt  water  instead  of  distilled  water,  and  the  fixed 
material  must  also  be  washed  in  salt  water.  Tissues  with  hard  or  very  firm 
cell  walls  are  improved  by  being  left  for  longer  periods,  perhaps  several 
days,  in  the  fluid,  for  the  chromic  acid  acts  on  the  cell  walls,  softening  them 
somewhat. 

Material  fixed  in  chrom-acetic  acid  must  be  washed  thoroughly  before 
being  carried  up  into  alcohol  for  final  preservation  (Sec.  178).  This  may  be 
done  most  satisfactorily  with  firm  tissues  in  a  gentle  stream  of  tap  water 
circulating  through  the  vessel  (a  wide-mouthed  bottle  with  a  piece  of  gauze 
tied  over  the  mouth  to  hold  the  material  within  is  convenient).  Washing 
may  occupy  several  hours  or,  with  firm  tissues,  a  much  longer  time  without 
danger.  It  is  necessary  to  get  all  of  the  chromic  acid  out  of  the  material, 
otherwise  a  precipitate  will  be  formed  by  the  alcohol  and  the  protoplasm 
will  not  stain  well. 

It  is  not  generally  known  that  the  chromic  acid  can  be  washed  out  by 
running  the  material  through  the  grades  of  alcohol  to  70%  (Sec.  178),  provided 
the  bottle  of  material  is  kept  in  the  dark.  The  precipitate  referred  to  in  the 
paragraph  above  is  only  formed  by  alcohol  in  the  presence  of  light.  The 
70%  alcohol  must  of  course  be  changed  until  there  is  no  trace  of  chromic 
acid.  This  method  works  especially  well  with  small  objects  and  saves 
much  time  and  the  somewhat  difficult  operation  of  washing  small  objects 
in  water. 

173.  Chrom-osmo-acetic  acid  (Flemming's  fluid).  The  most  successful  of  the 
formulae  containing  chromic,  osmic,  and  acetic  acids  were  developed  and 
perfected  by  Flemming  and  are  accordingly  called  Flemming's  fluids.  The 
addition  of  osmic  acid  to  the  chrom-acetic  basis  gives  somewhat  better 
fixation  of  material  than  chrom-acetic  acid  alone.  This  better  fixation 
appears  in  the  cytological  details  of  nuclear  division  and  in  a  more  brilliant 
reaction  of  material  to  the  stains  safranin  and  gentian  violet,  which  with 
orange  G  form  a  group  often  used  together  as  a  triple  stain  (Sec.  199,  D)  after 
this  fixing  agent.  Flemming's  fluids  penetrate  slowly,  and  material  should 
be  cut  up  into  small  pieces  or  slices,  perhaps  an  eighth  of  an  inch  in  thick- 
ness, to  obtain  the  best  results.  The  expense  of  the  osmic  acid  rather  pre- 
cludes the  use  of  these  fluids  for  general  morphological  and  histological 
studies  where  fortunately  the  cheap  chrom-acetic  formula^  are  in  the  main 
quite  satisfactory.  Flemming's  fluids  do  not  keep  in  the  light,  and  it  is  best 
to  make  them  up  fresh  just  before  fixation.  Solutions  of  osmic  acid  must  be 
kept  in  the  dark. 


194  BOTAXICAL  MICROTECHNIQUE 

A.  Weak  chrom-osmo-acetic  acid  {Weak  Flemming) : 

1%  chromic  acid        25  cc.  making  .25%  chromic  acid. 

1%  acetic  acid  10  cc.  making  .1%  acetic  acid. 

1%  osmic  acid  10  cc.  making  .1%  osmic  acid. 

distilled  water  55  cc. 

100  cc. 
This  well-known  formula  is  used  for  the  algse  and  fungi  and  delicate 
tissues  of  the  higher  plants.  It  has  the  same  strength  as  weak  chroni- 
acetic  acid  but  with  osmic  acid  added.  Half  the  amount  of  osmic  acid 
in  the  above  formula  gives,  according  to  our  experience,  better  results 
with  many  algse  and  fungi. 

B.  Strong  chrom-osmo-acetic  acid  (Strong  Flemming) : 

1%  chromic  acid  75  cc.  making  .75%  chromic  acid, 

glacial  acetic  acid  5  cc.  making  5%  acetic  acid. 

2%  osmic  acid  20  cc.  making  .4%  osmic  acid. 

100  cc. 
This  formula  has  a  medium  strength  of  chromic  acid  but  an  exceptional 
strength  of  acetic  and  osmic  acids.    It  may  easily  be  modified  by  vary- 
ing the  amounts  of  its  components.    Thus  Mottier  recommends  for 
anthers  the  following  proportions  :    1%  chromic  acid,  80  cc.  ;   glacial 
acetic  acid,  5  cc.  ;  2%  osmic  acid,  15  cc.    Strong  Flemming  naturally 
finds  its  use  on  the  same  sort  of  subjects  as  require  the  medium  or 
strong  formulae  of  chrom-acetic  acid,  as  for  example  the  firmer  tissues 
of  the  higher  plants. 
Material  fixed  by  Flemming's  fluids  must  be  washed  to  remove  the  chrom- 
acetic  acid,  as  described  in  the  previous  section.    The  osmic  acid  always 
blackens  the  material,  but  this  discoloration  is  not  treated  until  just  be- 
fore staining  (Sec.  198),  when  the  preparations  are  bleached  with  hydrogen 
peroxide.     The  chromic  acid  must  be  dissolved  in  sea  water,  when  these 
fluids  are  used  upon  marine  algee,   and  the  material  also  washed  in  sea 
water. 

174.  Absolute  alcohol.  The  fixing  fluids  based  on  chromic  acid  penetrate 
rather  slowly,  and  consequently  very  dense  tissues  or  structures  with  heavy 
hard  cell  walls  are  sometimes  not  at  all  well  fixed  by  them,  the  protoplasts 
appearing  shrunken.  There  is  also  occasional  difficulty  in  immersing  or 
wetting  material  in  these  water  solutions.  For  such  material  some  of  the 
fixing  fluids  based  on  alcohol  are  preferable.  The  best  of  these  are  absolute 
alcohol  and  Carnoy's  fluid. 

Absolute  alcohol  alone  is  not  an  especially  good  fixing  agent  except  for 
very  small  objects,  which  it  can  penetrate  almost  instantly.  Material  is,  of 
course,  ready  very  quickly  for  preservation  in  85%  alcohol,  or  for  the  process 
of  imbedding  in  paraffin. 


PRESERVATION   OF   MATERIAL  105 

175.  Carnoy's  fluid. 

absolute  alcohol  60  cc. 

chloroform  30  cc. 

glacial  acetic  acid  10  cc. 
100  cc. 
This  is  a  strong  fixing  fluid  which  penetrates  very  rapidly,  and  conse- 
quently should  only  be  used  for  a  few  minutes,  —  ten  to  tliirty  minutes  is 
probably  long  enough  for  most  subjects.  There  is  always  danger  of  leaving 
material  too  long  in  it.  The  material  is  washed  in  changes  of  absolute 
alcohol  until  there  is  no  odor  of  acetic  acid,  and  is  then  best  imbedded  at 
once,  but  may  be  transferred  to  85%  alcohol  for  preservation.  The  staining 
of  chromosomes  after  Carnoy's  fluid  is  sometimes  very  brilliant,  but  spindle 
fibers  and  other  kinoplasmic  structures  are  apparently  less  perfectly  preserved 
than  by  the  chrom-osmo-acetic  formula. 

If  the  subject  be  very  resistant  to  penetration,  as  for  example  the  mega- 
spores  of  the  pteridophytes,  the  proportionate  amount  of  acetic  acid  may  be 
greatly  increased.  Thus  two  parts  glacial  acetic  acid,  one  part  absolute 
alcohol,  and  one  part  chloroform  have  been  recommended  as  giving  good 
results  for  the  spores  of  Selaginella.  However,  even  in  these  cases,  long 
treatment  with  medium  or  strong  chrom-acetic  acid,  especially  if  applied 
hot,  aided  by  mechanical  cutting  or  pricking  of  material,  to  assist  penetration, 
will  frequently  give  better  results  than  Carnoy's  fluid. 

176.  Concluding  suggestions  on  fixing.  It  is  important  to  facilitate  mechan- 
ically, in  every  way  possible,  the  rapid  penetration  of  the  fixing  fluid.  Thus 
an  ovary  of  a  lily  should  be  pared  along  the  angles  and  then  sliced  in  pieces 
three  eighths  of  an  inch  thick  or  cut  lengthwise.  Small  objects,  such  as  fila- 
mentous algse,  may  be  examined  at  various  stages  in  the  process  of  fixation 
to  see  if  the  cell  contents  are  in  good  condition.  Material  that  must  be  sec- 
tioned cannot,  however,  be  so  easily  observed,  and  shrinkage  may  occur, 
which  was  not  caused  in  the  fixing,  but  at  some  later  stage  in  the  manipula- 
tion leading  to  sectioning  or  staining.  Consider  results  critically,  and  when 
unsatisfactory  attack  the  problem  as  one  of  physics  and  chemistry,  and  find 
just  where  the  methods  failed.  Close  attention  to  these  details  will  soon 
give  a  sure  command  of  a  few  simple  methods  of  fixing  which  are  likely  to 
give  satisfaction. 

THE  PRESERVATION  OF  MATERIAL 

177.  Alcohol.  Material  collected  for  general  morphological  study  may  be 
placed  at  once  in  95%  alcohol.  It  must  later  be  transferred  to  a  lower  grade, 
such  as  70%,  or  it  will  become  very  brittle.  Alcohol  mixed  with  glycerin, 
half  and  half,  or  one  fourth  glycerin,  will  keep  material  from  becoming 


196        .  BOTANICAL  MICROTECHNIQUE 

brittle,  and  is  especially  good  for  firm  structures  that  are  to  be  sectioned 
free-hand,  such  as  the  various  parts  of  seed  plants. 

Alcohol  is  the  best  all-round  preservative.  Other  fluids  have  appeared 
from  time  to  time  as  rivals,  as  for  example  formalin,  but  they  none  of 
them  have  supplanted  it.  It  is  somewhat  uncertain  whether  denatured 
alcohol,  now  on  the  market,  will  be  just  as  good  as  the  pure  alcohol  for 
preservative  purposes,  and  it  should  be  used  with  some  care  until  its  effects 
are  known. 

178.  Bringing  fixed  material  into  alcohol.  Botanists  are  coming  to  depend 
more  and  more  upon  fixed  material  even  for  general  morphological  studies, 
since  it  is  very  little  trouble  and  expense  to  fix  in  chrom-acetic  acid,  and 
the  superior  results  are  worth  the  attention  required.  This  is  especially  true 
of  type  material  of  the  thallophytes  and  bryophytes. 

Material  fixed  in  chrom-acetic  acid  or  in  chrom-osmo-acetic  acid  (Flem- 
ming's  fluids)  must  be  washed  as  described  in  Sec.  172,  and  then  passed,  or 
"run  up,"  through  several  grades  of  alcohol  to  70%  (or  85%  if  the  material 
is  delicate),  where  it  may  rest  indefinitely.  It  is  well  to  begin  with  15% 
alcohol  and  pass  successively  through  25%,  35%,  50%,  to  70%.  Small  objects 
such  as  lily  anthers  will  not  require  more  than  an  hour  in  the  lower  grades. 
They  should  remain,  however,  twice  as  long  in  the  35%  and  50%.  Larger 
objects  must  remain  from  four  to  eight  hours  in  each  grade.  The  process 
should  be  planned  so  that  material  is  not  left  for  so  long  a  time  as  over  night 
in  a  grade  of  alcohol  below  50%,  and  it  should  not  remain  in  50%  longer  than 
over  night.  Generally  the  entire  process  can  be  finished  in  one  day.  The 
grades  of  alcohol  are  made  from  95%,  which  for  general  purposes  is  regarded 
as  being  pure. 

Material  fixed  in  fluids  based  on  alcohol,  as  for  example  Carnoy's  fluid, 
should  be  passed  directly  into  a  grade  of  alcohol  corresponding  to  that  in  the 
fixing  fluid. 

179.  Formalin,  Much  was  expected  of  formalin  when  it  appeared  a  num- 
ber of  years  ago.  The  most  important  claims  have  not  been  fulfilled.  It  will 
not  preserve  the  green  color  of  plants  in  the  light,  and  shades  of  red,  blue, 
and  brown  are  generally  modified  after  a  few  months.  Unless  the  tissue  is 
firm  it  is  apt  sooner  or  later  to  soften  or  macerate  ;  this  is  especially  true  of 
the  lower  plants.  Finally,  formalin  is  intensely  disagreeable  to  work  with  on 
account  of  its  effect  on  the  nose  and  eyes. 

Formalin,  which  is  about  40%  formaldehyde,  is  added  to  water  to  make  a 
2-5%  solution.  It  is  convenient  to  carry,  since  a  small  quantity  will  make 
many  quarts  of  the  preserving  fluid.  If  material  is  to  be  used  within  a  short 
time,  formalin  will  prove  satisfactory.  Material  may  also  be  transferred  from 
formalin  to  alcohol,  being  carried  up  through  the  grades.  However,  its  ad- 
vantages are  rather  doubtful  when  chrom-acetic  acid  and  alcohol  are  at  hand. 


STAINS  197 

GENERAL  STAINING  METHODS 

180.  Methods  of  staining.  There  are  two  principal  methods  of  staining, — 
(1)  in  bulk  or  loose  sections,  and  (2)  on  the  slide.  The  second  method  gener- 
ally follows  the  process  of  sectioning  in  paraffin,  and  is  given  special  con- 
sideration in  Sees.  197-199.  Staining  in  bulk  is,  on  the  whole,  much  less 
precise  in  its  results  than  the  staining  of  microtome  sections.  The  methods 
of  staining  in  bulk  also  apply  to  sections  cut  free-hand  (Sec.  194),  either 
from  preserved  or  living  material. 

181.  Eosin.  Saturated  solutions  in  water  or  alcohol  are  used.  Material  is 
stained  almost  at  once,  and  should  then  be  transferred  to  1%  acetic  acid  for 
a  minute  (which  renders  the  stain  less  soluble),  after  which  the  acid  should 
be  thoroughly  washed  out.  Permanent  preparations  are  generally  made  in 
glycerin  after  the  method  outlined  in  Sec.  188.  If  the  preparations  are  to 
be  mounted  in  balsam  (Sec.  187),  the  staining  should  be  with  alcoholic  solu- 
tions, or,  better  still,  with  a  solution  in  absolute  alcohol  from  which  the 
material  may  pass  directly  into  xylol,  and  there  is  no  need  of  treatment 
with  acetic  acid. 

Eosin  does  not  stain  cell  walls  and  never  overstains  protoplasm.  It  is 
especially  useful  for  the  fungi,  which  are  generally  mounted  in  glycerin, 
and  is  one  of  the  best  of  the  quick,  simple  stains. 

182.  Iron-alum  haematoxylin.  This  method,  developed  by  Heidenhain, 
gives  the  most  satisfactory  results  of  all  the  hcematoxylin  stains  in  the  differ- 
entiation of  protoplasmic  structure.  Delafield's  haematoxylin  (Sec.  183)  is  a 
somewhat  better  stain  for  tissues,  because  it  colors  cell  walls  sharply.  Iron- 
alum  hsematoxylin  does  not  color  cell  walls  heavily,  and  is  consequently  a 
very  useful  general  stain  for  the  algse  and  fungi  which  are  to  be  stained  in 
bulk  and  mounted  without  sectioning. 

Two  separate  solutions  are  used  : 

(1)  A  2%  aqueous  solution  of  ammonia  sulphate  of  iron  (iron  alum). 

(2)  A  i%  solution  of  hsematoxylin  dissolved  in  hot  distilled  water. 

The  solution  of  iron  alum  acting  as  a  mordant  prepares  the  tissue  to  take 
up  the  hsematoxylin.  Bring  the  material  from  water  (running  it  down 
through  the  grades  of  alcohol,  if  preserved  in  the  latter)  into  the  iron-alum 
solution,  which  for  delicate  structures  may  be  diluted  to  l';^.  Leave  in  the 
iron  alum  from  one  to  three  hours,  rinse  for  a  few  minutes  in  water,  and 
place  in  the  hsematoxylin  solution.  If  the  hiematoxylin  becomes  too  muddy, 
replace  it  with  fresh.  Leave  the  material  in  the  haematoxylin  from  three  to 
ten  hours  (over  night  does  no  harm)  and  then  place  in  iron  alum  again.  The 
black  stain  extracts  rapidly,  and  the  material  must  be  examined  from  time 
to  time  under  the  microscope.  When  the  stain  has  been  extracted  to  the 
proper  point,  place  the  material  in  considerable  tap  water  for  a  half  hour,  or 


198  BOTANICAL  MICROTECHNIQUE 

as  much  longer  as  convenient,  to  remove  all  trace  of  the  iron  alum.  The 
material  is  now  ready  to  be  mounted  in  balsam  (Sec.  187)  or  glycerin 
(Sec.  188).  If  mounted  in  balsam  it  must  be  carried  through  xylol  (never 
oil  of  cloves,  which  fades  hematoxylin). 

The  hsematoxylin  can  be  extracted  to  a  point  where  the  nucleus  is  prac- 
tically the  only  structure  stained,  and  is  consequently  one  of  the  best  of 
the  nuclear  stains.  Such  material  may  be  counterstained  (that  is,  stained 
in  addition)  with  safranin  (Sec.  184),  thus  differentiating  the  nucleus  (gray 
or  black)  from  the  rest  of  the  protoplasm  (red).  Iron -alum  hsematoxylin  is 
probably  on  the  whole  the  most  satisfactory  of  all  the  staining  methods  for 
protoplasmic  structures.  It  is  subject  to  great  latitude  in  the  time  limits, 
which  may  be  set  for  the  different  stages  of  the  process  except  that  of  extrac- 
tion, which  must  of  course  be  watched  carefully ;  but  these  are  soon  learned 
with  experience.  It  is  perhaps  the  least  uncertain  of  the  stains,  and  although 
the  process  is  somewhat  long  it  can  always  be  depended  upon  to  give 
good  results. 

183.  Delafield's  haematoxylin.  This  stain  reacts  very  differently  from  iron- 
alum  haematoxylin.  It  stains  cell  walls  sharply,  but  does  not  differentiate 
protoplasmic  structures  as  well  as  the  latter.  It  is  one  of  the  best  stains  for 
tissues  of  higher  plants,  and  may  be  combined  very  effectively  with  safranin, 
as  described  below  and  in  Sec.  185. 

Delafield's  hsematoxylin  is  made  as  follows :  a  solution  of  1  gram  haema- 
toxylin in  6  cc.  absolute  alcohol  is  added  drop  by  drop  to  100  cc.  of  a 
saturated  solution  of  ammonia  alum.  Filter  after  exposing  for  a  week  to 
the  air  and  light.  Then  add  25  cc.  of  glycerin  and  25  cc.  of  methyl  alcohol. 
Allow  the  mixture  to  stand  for  several  hours  (4-7),  until  the  color  is  dark, 
and  then  filter.  The  solution  should  then  remain  two  months  in  a  tightly 
stoppered  bottle  to  "ripen."  The  prepared  stain  may  be  purchased  from 
dealers  (Sec.  218). 

Material  is  transferred  to  Delafield's  hematoxylin  from  water  or  25% 
alcohol.  Staining  will  take  place  rather  rapidly,  requiring  from  a  few  min- 
utes to  an  hour  or  more.  The  stain  may  be  diluted  to  half  or  a  fourth  of 
the  above  strength,  and  the  staining,  although  longer,  is  frequently  better. 
Wash  the  material  in  tap  water  until  a  rich  purple  color  develops.  If  the 
sections  or  other  subjects  are  overstained,  or  if  a  precipitate  is  formed  when 
the  material  is  placed  in  alcohol,  rinse  in  acid  alcohol  {j^^  cc.  hydrochloric 
acid  in  100  cc,  70%  alcohol).  The  acid  alcohol  takes  out  the  color,  which 
may  thus  be  extracted  until  the  nucleus  alone  remains  stained.  When 
washed  in  acid  alcohol  the  material  must  be  placed  in  tap  water  until  the 
purple  color  returns.  Then  run  up  in  the  grades  of  alcohol  through  95% 
and  absolute  alcohol,  clear  in  xylol,  and  mount  in  balsam,  as  described  in 
Sec.  187,  or  pass  from  water  into  glycerin,  as  outlined  in  Sec.  188. 


STAINS  199 

Material  stained  in  DelafieJcPs  ha^matoxylin  may  be  counterstained  with 
alcoholic  safranin,  but  very  good  results  may  be  obtained  with  the  tissues  of 
higher  plants  by  staining  first  with  safranin,  as  described  in  Sec.  185. 

184.  Safranin.  There  are  various  kinds  of  safranin  sold,  some  of  which 
dissolve  more  readily  in  water  and  some  in  alcohol.  The  stain  should  always 
bfe  placed  in  its  appropriate  solvent.  A  1%  solution  in  water  is  a  good 
strength,  and  a  saturated  solution  in  95%  alcohol  mixed  with  an  equal  vol- 
ume of  water,  making  a  50%  alcoholic  solution,  is  also  good.  The  alcohol 
solutions  are  the  most  convenient.  Anilin  safranin  is  prepared  from  a  satu- 
rated solution  in  95%  alcohol  mixed  with  an  equal  amount  of  anilin  water 
(made  by  shaking  anilin  oil  in  distilled  water,  when  a  small  percentage  of 
the  oil  is  taken  up  by  the  water).  Anilin  safranin  is  considered  by  some 
to  be  the  best  of  the  safranin  stains. 

Safranin  colors  cell  walls  as  well  as  protoplasm.  It  is  therefore  a  general 
stain,  but  when  properly  extracted  it  may  be  made  to  differentiate  certain 
nuclear  structures  sharply  (chromosomes  and  nucleolus),  and  is  much  used 
in  staining  on  the  slide,  especially  in  combination  with  gentian  violet  and 
orange  G  (Sec.  199,  D).  Material  may  remain  in  safranin  from  one  hour  or 
less  to  twelve  hours  or  more.  The  stain  is  extracted  in  50%  alcohol  until  the 
desired  coloration  is  obtained,  or,  if  very  much  overstained,  the  material  may 
be  placed  in  acid  alcohol  (yV  cc.  hydrochloric  acid  in  100  cc.  70%  alcohol). 
The  acid  alcohol,  if  used,  must  be  thoroughly  washed  out. 

185.  Safranin  and  Delafield's  haematoxylin.  Safranin  followed  by  Delafield's 
hsematoxylin  is  an  excellent  stain  for  the  tissues  of  higher  plants,  whether 
in  free-hand  or  microtome  sections.  Sections  cut  free-hand  from  fresh 
material  may  be  fixed  for  10-15  minutes  in  absolute  alcohol  or  medium 
chrom-acetic  acid  (Sec.  194) ;  those  from  preserved  material  may  be  stained 
at  once.  They  should  remain  in  the  safranin  several  hours  (over  night). 
Wash  in  50%  alcohol  (acid  alcohol  if  desired)  until  the  stain  is  extracted 
from  all  parts  except  lignified  cell  walls,  as  in  fibro-vascular  bundles. 
Remove  the  acid  alcohol  if  used.  Stain  in  Delafield's  ha-matoxylin  for 
several  minutes  (1-30).  AVash  in  tap  w-ater,  or  extract  the  stain  if  necessary 
in  acid  alcohol  (as  described  in  Sec.  183),  which  must  be  followed  by  tap 
water  until  the  stain  is  purple.  Carry  through  95%  alcohol,  then  absolute 
alcohol,  clear  in  xylol,  and  mount  in  balsam.  Sections  cut  on  the  microtome 
are  stained  on  the  slide  (Sec.  197)  in  the  same  manner  as  described  above. 

186.  Other  anilin  stains.  There  are  numerous  anilin  dyes  of  great  value 
in  special  cases,  but  few  of  them  have  such  general  usefulness  as  eosin, 
safranin,  and  gentian  violet.    The  following,  however,  are  important. 

A.  Acidfuchsln.  A  1%  solution  may  be  made  in  water  or  in  70';  alcohol. 
The  stain  acts  rapidly  and  is  very  brilliant.  It  may  be  extracted  in 
95%  alcohol  from  overstained  material  or  sections. 


200  BOTANICAL  MICROTECHNIQUE 

B.  Methyl  green.  A  saturated  solution  in  1%  acetic  acid  keeps  well,  or  it 
may  be  made  up  simply  in  distilled  water.  Dilute  if  desired.  This  is 
a  good  stain  for  living  cells,  but  it  is  especially  valuable  in  combination 
with  acid  fuchsin,  forming  an  effective  double  stain  for  the  tissues  of 
higher  plants.  Sections  from  preserved  material  may  be  stained  at  once, 
those  from  fresh  material  must  be  fixed  in  absolute  alcohol  or  chrom- 
acetic  acid  (Sec.  194).  Stain  first  with  methyl  green  for  two  hours  or 
more  and  wash  in  distilled  water  until  the  green  remains  in  the  ligni- 
fied  cell  walls  alone.  Then  stain  with  acid  fuchsin  for  a  few  minutes, 
—  not  long  enough  to  affect  the  lignified  tissues,  —  and  pass  through 
95%  alcohol  to  absolute  alcohol  and  into  clove  oil  and  balsam  (Sec.  187). 

C.  Erythrosin.  This  stain  is  similar  to  eosin  and  may  be  used, in  saturated 
solutions  in  water  or  70%  alcohol.  It  is  a  good  counterstain  following 
haematoxylin  or  green  and  blue  anilin  dyes. 


MOUNTING  IN  BALSAM  AND  GLYCERIN 

187.  Mounting  in  balsam,  Canada  balsam  is  the  most  satisfactory  medium 
for  permanent  preparations.  It  should  be  used  whenever  possible,  but  there 
are  some  subjects,  such  as  delicate  filamentous  algse  and  fungi,  which  cannot 
easily  be  carried  into  balsam  without  shrinkage,  or  which  cannot  be  teased 
apart  when  brought  into  that  medium  because  the  clearing  agents  such  as 
xylol  or  clove  oil  render  the  filaments  much  less  flexible.  For  such  subjects 
glycerin,  glycerin  jelly,  or  Venetian  turpentine  are  better  media. 

Material  is  carried  into  balsam  from  absolute  alcohol  through  a  clear- 
ing agent.  It  must  first  be  brought  up  through  the  grades  of  alcohol  to  95% 
(Sec.  178),  where  it  is  best  left  several  hours  (it  may  remain  in  95%  alco- 
hol indefinitely).  Material  is  then  placed  in  absolute  alcohol  to  remove  all 
trace  of  water  (dehydration).  Dehydration  takes  from  thirty  minutes  to 
an  hour  or  more,  according  to  the  size  of  the  object,  and  it  is  well  to  change 
the  alcohol  once  or  twice  if  there  is  much  material.  From  absolute  alcohol 
the  material  is  carried  into  a  clearing  agent,  clove  oil  or  xylol  being  the 
simplest.  Clove  oil  removes  the  absolute  alcohol  rapidly  and  is  the  better 
clearing  agent  following  anilin  dyes,  but  should  never  be  used  after  hcBmatoxy- 
lln,  for  its  acid  quality  fades  that  stain.  Xylol  acts  more  slowly  and  does  not 
affect  hsematoxylin  stains.  Microtome  sections  on  the  slide  are  handled 
much  more  rapidly  through  the  alcohols  and  clearing  agents,  as  is  described 
in  Sec.  199. 

With  delicate  material  xylol  is  always  the  safest  clearing  agent,  because 
it  mixes  more  slowly  and  less  violently  with  absolute  alcohol.  The  danger  of 
shrinkage  is  lessened  greatly  by  preparing  three  mixtures  of  absolute  alcohol 


MOUNTINCI  IN   BALSAM  AND  (iLYCKUlN  201 

and  xylol  :  (1)  one  fourth  xylol  and  three  fourths  absolute  alcohol  ;  (li)  iialf 
and  half  xylol  and  absolute  alcohol ;  (3)  three  fourths  xylol  and  one  fourth 
absolute  alcohol.  Even  the  most  delicate  material  of  algic  and  fungi  can 
generally  be  carried  without  shrinkage  into  pure  xylol  if  passed  through 
these  grades,  being  left  an  hour  or  more  in  each.  Once  in  xylol,  material  is 
safe  from  shrinkage,  and  it  may  be  left  in  this  reagent  indefinitely.  It  is 
absolutely  essential  for  good  results  that  the  dehydration  be  perfect.  Small 
objects  should  be  examined  throughout  the  process  to  determine  the  exact 
time  of  any  cell  shrinkage,  which  may  be  corrected  with  greater  care. 

After  being  in  clove  oil  a  short  time  (from  five  to  fifteen  minutes),  or 
in  xylol  a  much  longer  time  (several  hours),  tlie  material  is  transferred  to 
Canada  balsam  on  the  slide.  The  balsam  should  be  so  diluted  with  xylol 
that  it  drops  readily  from  a  glass  rod.  A  cover  glass  is  then  gently  lowered 
over  the  object  with  the  point  of  a  needle.  The  balsam  will  gradually  harden 
as  the  xylol  dries  out.  Air  bubbles  need  give  no  concern  ;  they  will  work 
out  to  the  edge  of  the  cover  glass  as  the  balsam  hardens.  When  balsam 
thickens  in  its  bottle  xylol  should  be  added  ;  the  cloudiness  which  may 
develop  will  soon  pass  away. 

188.  Mounting  in  glycerin.  Material  is  transferred  from  water  to  a  con- 
siderable quantity  of  a  10%  aqueous  solution  of  glycerin  in  a  watch  glass. 
This  should  not  cause  shrinkage.  The  watch  glass  is  then  protected  from 
dust  and  the  water  allowed  to  evaporate  until  the  solution  is  about  as  thick 
as  pure  glycerin.  The  material  is  now  ready  to  be  mounted  and  will  be  so 
soft  that  it  can  be  easily  teased  apart.  A  small  drop  of  the  solution  is  placed 
on  the  slide,  the  material  arranged  in  it,  and  a  clean  cover  glass  with  one 
edge  resting  on  the  slide  is  carefully  lowered  with  a  needle  until  the  glycerin 
runs  out  to  the  edge  on  all  sides.  This  must  be  done  so  carefully  that  no 
bubbles  of  air  are  inclosed. 

Practice  will  determine  the  amount  of  glycerin  necessary  to  fill  the  space 
under  the  cover  glass,  which  should  not  be  more  than  five  eighths  the  width 
of  the  slide.  The  less  glycerin  the  better.  The  glycerin  should  not  run 
out  beyond  the  edge  of  the  cover  glass,  although  a  small  amount  may  be 
wiped  away  with  a  cloth  moistened  in  alcohol.  On  no  account  umst  the 
glycerin  be  allowed  to  run  over  the  edge  of  the  cover  glass ;  such  a  prepara- 
tion is  worthless.  The  slide  is  now  ready  to  be  sealed,  or  it  may  be  laid  away 
to  allow  the  glycerin  to  become  somewhat  more  dense. 

The  best  cement  is  gold  size.  This  should  not  be  so  thick  that  it  cannot 
be  easily  spread  with  a  brush.  If  too  thick,  thin  with  oil  of  turpentine.  The 
gold  size  is  generally  applied  at  the  edge  of  the  cover  glass  while  the  slide  is 
whirling  on  a  turntable.  A  thin  ring  should  be  laid  three  eighths  of  an  inch 
wide,  half  on  the  slide  and  half  over  the  edge  of  the  cover  glass,  thus  seal- 
ing the  glycerin  within  a  chamber.    The  sealing  will  not  be  perfect  unless 


202  BOTANICAL  MICROTECHNIQUE 

the  cover  glass  and  slide  are  absolutely  dry,  that  is,  free  from  any  glycerin. 
The  first  ring  should  be  thin  and  allowed  to  dry  thoroughly  before  the  second 
ring  is  applied.  More  may  be  added  if  necessary.  Properly  sealed  prepara- 
tions will  last  indefinitely,  but  the  sealing  is  a  delicate  operation  and  re- 
quires some  experience. 

Glycerin  jelly  is  for  some  subjects  as  good  a  mounting  medium  as  glycerin, 
and  the  preparations  are  more  durable.  Transfer  material  from  a  rather 
thick  solution  of  glycerin  to  a  drop  of  melted  jelly  on  a  warm  slide,  arrange 
with  needles  and  carefully  lower  a  warm  cover  glass  over  the  mount,  taking 
care  not  to  inclose  air  bubbles.  It  is  necessary  to  work  quickly.  The  cover 
glass  may  be  sealed  with  a  ring  of  gold  size  and  thus  strengthened. 

189.  Venetian  turpentine.  The  difificulty  of  properly  sealing  glycerin 
preparations,  together  with  their  fragile  nature,  is  the  chief  objection  to  the 
glycerin  mount.  A  method  of  mounting  in  Venetian  turpentine  has  recently 
been  perfected  by  Chamberlain,  i  By  this  process  material  may  be  brought 
without  danger  of  shrinkage  into  a  medium  (Venetian  turpentine)  which 
hardens  like  balsam  and  requires  no  sealing.  The  technique  is  somewhat 
long  and  the  staining  methods  special,  but  the  results  are  striking.  The 
staining,  so  far  as  we  have  seen  preparations,  does  not  bring  out  the  finest 
details  of  protoplasmic  structure  as  well  as  such  stains  as  iron-alum  hsematox- 
ylin,  safranin,  and  gentian  violet.  For  details  of  this  method  the  reader  is 
referred  to  Chamberlain. 


IMBEDDING  IN  PARAFFIN 

190.  The  paraffin  method  of  sectioning.  There  are  several  methods  of  sec- 
tioning plant  tissue,  all  of  which  have  their  limitations,  because  plant  struc- 
tures range  from  those  of  great  delicacy,  as  among  the  thallophytes  and 
bryophytes,  to  the  firm  and  hard  tissues  of  the  sporophyte  generation  of  the 
pteridophytes  and  sperm atophytes.  Very  firm  or  hard  tissue  cannot  be  cut 
in  paraffin,  and  sections  may  be  made  free-hand  (Sec.  194)  from  fresh  or  pre- 
served material,  but  are  better  cut  in  celloidin  (Sec.  195).  Softer  structures, 
such  as  anthers,  ovule  cases,  and  many  developing  organs  of  the  seed  plants, 
together  with  the  gametophyte  generations  of  the  pteridophytes  and  almost 
all  structures  in  the  bryophytes  and  thallophytes,  are  sectioned  most  effect- 
ively by  the  paraffin  method.  Its  advantages  are  that  sections  can  be  cut 
very  thin,  that  they  can  easily  be  arranged  serially  on  the  slide,  and  that 
they  can  be  stained  with  greater  precision.  Sectioning  in  paraffin  is  pre- 
ceded by  the  process  of  imbedding,  which  involves  the  preliminary  processes 
of  dehydration  and  clearing,  and  initltration. 

1  Methods  of  Plant  Histology,  p.  79,  1905. 


IMBEDDTNG  IN  PARAFFIN  203 

191.  Dehydration  and  clearing.  The  material  to  be  cut  is  passed  carefully 
through  the  grades  of  alcohol  to  95%  (Sec.  17H).  It  should  remain  in  96%  alco- 
hol for  at  least  several  hours  or  more,  and  is  then  placed  in  absolute  alcohol, 
generally  in  a  vial,  and  this  should  be  poured  off  and  renewed  after  an  hour 
or  two.  The  material  should  be  left  in  absolute  alcohol  from  four  to  eight 
hours  or  over  night,  unless  t^e  object  be  very  small.  It  ought  then  to  be  free 
fiom  water  (dehydrated)  and  ready  for  the  clearing  agent,  which  will  remove 
the  absolute  alcohol  and  also  dissolve  the  paraffin,  so  that  the  latter  may  re- 
place the  former  throughout  the  tissue.  The  clearing  agents  most  frequently 
used  are  chloroform  and  xylol.  Chloroform  acts  more  rapidly,  but  there  is 
less  danger  of  shrinkage  with  xylol.  However,  the  chief  danger  of  shrinkage 
lies  in  imperfect  dehydration. 

Three  mixtures  of  the  clearing  agent  (chloroform  or  xylol)  with  absolute 
alcohol  are  necessary  to  insure  the  gradual  replacement  of  the  latter  by  the 
former.  These  are  (1)  one  fourth  clearing  agent,  three  fourths  absolute 
alcohol ;  (2)  half  and  half  clearing  agent  and  absolute  alcohol ;  (3)  three 
fourths  clearing  agent  and  one  fourth  absolute  alcohol.  The  material  ic 
passed  through  these  mixtures  in  the  above  order  and  then  into  the  pure 
clearing  fluid,  either  chloroform  or  xylol.  When  chloroform  is  used  the 
material  need  not  be  left  more  than  from  four  to  eight  hours  in  each  mixture, 
and  less  if  the  object  be  small.  If  xylol  is  used,  the  material  should  be 
left  at  least  twelve  hours  in  each  mixture,  and  a  longer  time  will  do  no  harm. 
It  should  not  remain  in  pure  chloroform  more  than  twelve  hours  before 
paraffin  is  added,  and  a  shorter  time  is  generally  better ;  but  it  may  be 
left  in  pure  xylol  a  longer  time,  and  even  a  day  or  more  with  advantage. 
Besides  removing  the  absolute  alcohol  the  clearing  agent  renders  the  tissues 
more  transparent,  that  is,  "clears"  them. 

192.  Infiltration.  Small  pieces  of  paraffin  are  now  added  to  the  chloroform 
or  xylol  to  the  point  of  saturation  and  beyond.  At  this  time  the  vials  may 
be  placed  on  the  top  of  the  oven,  where  they  will  be  warmed,  thus  allowing 
more  paraffin  to  dissolve. 

The  best  form  of  paraffin  bath  is  a  square  or  rectangular  hot-water  oven, 
with  a  door  at  the  side  and  one  or  more  shelves  within.  This  should  be 
heated  by  gas  or  by  an  electric  coil  with  a  thermostat  arrangement  to  keep 
the  oven  at  a  constant  temperature  of  about  52°  C.  The  temperature  may 
run  as  high  as  56°,  or  probably  higher  if  the  dehydration  has  been  jierfect, 
but  in  general  the  temperature  should  be  kept  low. 

Material  in  chloroform  and  paraffin  is  placed  in  the  bath  and  the  vial  un- 
corked. The  chloroform  will  be  driven  off  after  a  number  of  hours,  leaving 
the  material  in  pure  melted  paraffin.  This  process  should  not  be  hastened  ;  a 
day  or  two  in  the  paraffin  bath  will  generally  give  the  most  satisfactt)ry  results. 
Tasting  the  paraffin  is  the  best  test  of  the  removal  of  the  chloroform  ;  should 


204  BOTANICAL  MICROTECHNIQUE 

it  be  at  all  sweet  there  is  chloroform  still  present.  The  chloroform  must  be 
entirely  driven  off  before  imbedding,  otherwise  the  paraffin  will  not  cut  well. 

Material  in  xylol  and  paraffin  must  be  treated  differently  from  that  in 
chloroform.  Xylol  cannot  be  removed  easily  by  heat.  Consequently  the  ma- 
terial must  be  transferred  through  solutions  with  less  xylol  in  them  until  it  is 
carried  into  pure  paraffin.  The  simplest  way  is  to  pour  off  solutions  and  add 
melted  paraffin,  keeping  the  vials  in  the  bath.  The  mixtures  of  paraffin  and 
xylol  may  be  saved  and  used  again  or  simply  left  in  the  bath  to  gradually 
purify  as  the  xylol  is  driven  off.  Finally  the  material  is  placed  in  two  or 
three  changes  of  pure  paraffin  to  remove  the  last  trace  of  xylol.  It  will  do 
the  material  no  harm  to  remain  several  days  in  the  mixtures  of  paraffin  and 
xylol,  and  structures  with  thick  walls  or  coats  (such  as  the  megaspores  of 
Selaginella)  must  be  left  sometimes  for  weeks  before  infiltration  is  completed. 

193.  Imbedding.  The  material  is  now  in  pure  melted  paraffin  and  ready 
to  be  cast  in  a  cake.  Most  subjects  can  be  cut  in  paraffin,  which  melts  at  a 
relatively  low  temperature,  50°-52°  C.  Others  require  a  hard  paraffin  with 
a  melting  point  of  56°  or  higher.  In  general  it  is  better  to  imbed  in  a  medium 
paraffin  and  plan  to  cut  in  a  room  at  a  cool  temperature. 

Petri  dishes  are  good  receptacles  for  the  casting,  or  paper  trays  may  be 
used.  Two  L-shaped  pieces  of  metal  on  a  glass  plate  are  convenient,  since 
the  size  of  the  mold  may  be  readily  adjusted  to  the  object.  The  interior  of 
the  receptacle  should  be  smeared  with  glycerin  to  prevent  the  paraffin  from 
sticking.  The  melted  paraffin  is  poured  into  the  receptacle  with  the  material 
and  the  latter  is  then  arranged  with  a  heated  needle.  Finally  the  receptacle 
is  gently  lowered  into  a  vessel  of  cold  water,  so  that  the  paraffin  is  cooled 
quickly,  which  prevents  its  crystallizing,  but  it  cannot  be  entirely  immersed 
until  the  paraffin  has  solidified  over  the  top.  When  cold,  the  cake  may  be 
cut  up  into  blocks  of  convenient  size  which  are  ready  for  cutting  (Sec.  196). 
Material  that  is  perfectly  imbedded  will  be  preserved  indefinitely  in  a  form 
that  gives  no  further  trouble,  and  for  this  reason  it  is  often  desirable  to  run 
material  into  paraffin  instead  of  keeping  it  in  alcohol. 


SECTIONING 

194.  Free-hand  sectioning.  Free-hand  sections  are,  as  a  rule,  sufficiently 
satisfactory  for  general  studies  of  the  tissues  of  spermatophytes  and  pterido- 
phytes.  The  technique  is  as  follows.  The  object  is  held  between  the  thumb 
and  finger  of  the  left  hand,  or,  if  small  or  soft,  it  must  be  placed  between  two 
flat  pieces  of  pith.  The  razor  is  held  in  the  right  hand  and  is  drawn  across 
the  object  with  the  edge  towards  the  operator  and  the  blade  sliding  on  the 
forefinger  of  the  left  hand.    There  should  be  water  on  the  upper  edge  of  the 


SECTIONING  205 

razor,  and  as  the  sections  are  cut  they  should  slip  into  the  water  and  float 
in  it.  When  a  number  of  sections  have  been  cut,  they  may  be  removed  with 
a  brush  to  a  watch  glass  of  water.  It  is,  of  course,  impossible  to  cut  good 
sections  with  a  dull  razor. 

A  small  hand  or  table  microtome  is  frequently  of  great  assistance,  taking 
the  place  of  free-hand  sectioning.  The  object  is  held  between  pith  in  an 
adjustable  clamp,  and  the  razor  slides  over  a  glass  plate.  A  large  number  of 
sections,  sufficient  to  supply  a  class,  may  thus  be  easily  cut  from  such  an 
object  as  a  piece  of  stem  or  leaf. 

Some  methods  of  staining  free-hand  sections  have  been  outlined  in  Sees. 
183-186.  Those  of  preserved  material  in  alcohol  require  no  further  treatment 
before  being  placed  in  the  stain,  but  sections  of  living  material  must  be  fixed 
before  they  can  be  satisfactorily  stained.  If  the  tissue  is  firm,  the  simplest 
method  is  to  place  the  sections  directly  into  absolute  alcohol,  when  after  an 
hour  or  so  they  may  be  stained.  If,  however,  the  tissue  is  delicate,  or  the  cells 
contain  much  protoplasm,  it  is  best  to  fix  in  medium  chrom-acetic  acid  (Sec.  172) 
for  two  to  twelve  hours,  washing  for  an  hour  or  more  in  several  changes  of 
water.    Such  sections  may  be  stained  at  once  or  run  up  into  alcohol. 

195.  Sectioning  in  celloidin.  As  previously  stated  (Sec.  190),  very  firm  and 
hard  tissues  such  as  characterize  the  sporophyte  generation  of  pterido- 
phytes  and  spermatophytes  cannot  be  cut  in  paraffin.  Exact  work  is  fre- 
quently only  possible  through  sections  cut  in  celloidin.  Furthermore,  large 
sections  of  stems,  roots,  etc.,  can  only  be  cut  by  this  method.  The  tech- 
nique is,  however,  somewhat  long,  and  for  the  purposes  of  general  studies 
f-ree-hand  sections,  or  those  cut  on  a  hand  microtome,  are  likely  to  prove 
sufficiently  satisfactory.  A  detailed  account  of  the  celloidin  method  as  em- 
ployed in  botany  is  given  by  Plowman,  Botanical  Gazette,  Vol.  XXXVII, 
p.  450,  1904  ;  and  in  Chamberlain's  Methods  of  Histology. 

196.  Sectioning  in  paraffin.  Sectioning  in  paraffin  is  only  possible  for 
structures  of  reasonably  soft  tissue  and  not  very  large.  The  advantages  of 
the  method  are  that  the  sections  may  be  cut  much  thinner  than  in  celloidin 
or  free-hand,  that  they  may  easily  be  arranged  serially,  and  that  they  may 
be  stained  with  greater  precision.  The  method  is  very  generally  applicable 
throughout  the  thallophytes  and  bryophytes  and  for  the  gametophyte  gen- 
eration of  the  pteridophytes  and  spermatophytes,  together  with  the  softer 
tissues  of  many  organs  and  developing  structures  of  the  sporophyte  genera- 
tion of  the  latter  groups. 

Paraffin  material  is  cut  on  a  microtome.  The  most  convenient  instru- 
ment is  the  rotary  microtome  of  the  Minot  type,  of  which  there  are  several 
forms  on  the  market.  The  sliding  microtome  of  the  Jung-Tlioma  type  is 
also  excellent,  and  while  not  so  rapid  as  the  rotary  is  sometimes  more  accu- 
rate for  the  most  exact  work. 


206  BOTANICAL  MICROTECHNIQUE 

The  material,  imbedded  in  the  paraffin  cake,  is  cut  out  in  a  small  block, 
which  is  fastened  by  heat  to  a  metal  holder  for  the  rotary  microtome  or  to 
small  wooden  holders  for  the  sliding  ones.  The  block  should  be  arranged  so 
that  it  will  be  cut  as  nearly  as  possible  in  the  correct  plane.  The  paraffin 
is  then  trimmed  around  the  object  so  that  the  cutting  edge  is  square  or  rec- 
tangular, with  parallel  edges.  The  block  is  then  adjusted  by  a  mechanism  so 
that  the  face  which  is  to  strike  the  knife  is  exactly  parallel  to  its  edge  and  so 
that  the  object  will  be  cut  in  the  desired  plane. 

Cutting  in  paraffin  is  not  successful  unless  the  sections  run  off  the  knife 
edge  in  an  unbroken  ribbon.  There  are  a  number  of  conditions  necessary 
to  obtain  this  result.  The  knife  must  be  very  sharp  and  the  edge  without 
nicks  (at  least  where  the  cutting  is  done),  which  will  split  the  ribbon 
lengthwise.  It  is  useless  to  attempt  to  cut  with  a  poor  or  dull  knife.  If  a 
ribbon  after  running  smoothly  begins  to  split  or  show  conspicuous  lines, 
draw  the  finger  upwards  along  the  edge  of  the  knife.  The  difficulty  may 
have  been  caused  by  some  hard  particle  lodged  against  the  edge,  which  is 
thus  removed.  The  edge  of  the  knife  must  be  clean  ;  grease  or  paraffin  may 
be  removed  with  xylol  applied  by  a  brush  or  with  a  soft  rag. 

The  ribbon  should  run  straight.  If  it  begins  to  curve,  trim  the  block 
unevenly  so  that  it  will  come  off  the  knife  straight ;  a  curved  ribbon  is 
generally  due  to  differences  in  the  texture  of  the  two  sides  of  the  object. 
Sometimes  sections  roll  up  or  fail  to  stick  together  in  a  ribbon.  This  gen- 
erally means  that  the  paraffin  is  too  hard  for  the  temperature  of  the  room. 
The  cutting  must  be  done  in  a  warmer  room  or  the  material  reimbedded 
in  a  softer  paraffin.  Cutting  the  sections  in  the  sunshine  of  a  window 
instead  of  in  the  shade  will  often  remedy  the  difficulty.  A  more  fre- 
quent difficulty  is  a  crushing  of  the  sections  together.  This  means  either 
that  the  knife  is  not  sharp,  that  its  edge  is  not  perfectly  clean,  or  that  the 
paraffin  is  too  soft  for  the  temperature  of  the  room.  If  the  paraffin  is  too 
soft  (as  is  commonly  true  in  summer  temperatures),  the  block  and  knife  may 
be  cooled  in  ice  water  or  the  material  reimbedded  in  harder  paraffin.  It  is 
time  wasted  to  attempt  to  cut  when  the  ribbon  is  not  running  smoothly; 
find  out  where  the  trouble  lies  and  remedy  it. 

The  finest  quality  of  hone  is  necessary  for  sharpening  microtome  knives, 
and  it  should  never  be  used  for  any  other  purpose.  The  Belgian  stones  are 
the  best.  There  are  also  some  good  carborundum  hones.  The  razor  is 
gently  passed  back  and  forth  on  the  hone  with  the  edge  forward,  and  strop- 
ping is  not  necessary  or  desirable  if  the  hone  is  of  the  best  quality.  Soapy 
water  is  one  of  the  best  lubricants  of  the  hone. 

Sections  are  best  cut  from  7-10  micromillimeters  thick  for  general  histo- 
logical work,  but  nuist  be  cut  5  or  less  for  the  finest  details  of  protoplasmic 
structure.    A  micromillimeter  (also  called  a  micron)  is  a  thousandth  of  a 


STAli\IN(;   ()\    J'HK  .SLIDE  207 

millimeter.  As  the  ribbon  comes  off  the  microtome  knife  it  is  removed  in 
convenient  lengths  and  laid  in  a  series  from  left  to  right  on  a  clean  piece  of 
paper.  The  ribbons  may  be  kept  indefinitely  under  a  bell  jar,  but  they  are 
best  mounted  as  soon  as  convenient,  since  they  will  collect  some  dust  no 
matter  what  precautions  are  taken. 

The  ribbons  are  made  to  adhere  to  the  slide  with  a  fixative  of  the  follow- 
ing formula  (Mayer's  albumen  fixative) : 

white  of  egg  50  cc. 

glycerin  50  cc. 

sodium  salicylate  1  gram 
Mix  well  and  filter.  The  sodium  salicylate  is  an  antiseptic  and  the  fixative 
will  keep  for  several  months.  Place  a  very  small  drop  on  the  slide  and  with 
the  tip  of  the  little  finger  spread  the  thinnest  film  that  can  be  laid  on  evenly 
over  it.  Then  cover  the  film  of  fixative  with  water  and  place  the  ribbons 
cut  to  the  proper  lengths  upon  the  water,  arranged  as  desired.  Warm  the 
water  gently  over  a  flame ;  the  paraffin  will  soften  and  the  ribbons  will 
expand  and  become  perfectly  smooth.  The  paraffin  should  not  be  allowed 
to  melt.  Drain  the  water  off  carefully  and  arrange  the  ribbons,  which  will 
now  lie  in  a  film  of  water,  over  the  fixative.  Put  the  slide  aside  to  dry.  It 
is  frequently  convenient  to  warm  the  ribbons  in  the  water  by  placing  the 
slide  on  the  top  of  the  paraffin  bath  and  then  to  dry  the  slide  in  the  same 
way,  protected  from  too  much  heat  by  several  thicknesses  of  blotting  paper. 
The  preparations  are  not  ready  for  staining  on  the  slide  until  perfectly 
dry.  They  may  be  kept  thus  indefinitely,  but  it  is  best  to  stain  soon, 
since  the  surface  of  the  ribbons  will  inevitably  collect  dust.  A  great  saving 
of  time  can  be  secured  by  preparing  a  number  of  slides  at  a  time  and  carry- 
ing them  simultaneously  through  the  above  processes  and  those  of  staining 
on  the  slide. 

STAINING  ON  THE  SLIDE 

197.  Preparation  for  staining  on  the  slide.  The  dry  slides  with  the  ribbons 
adhering  to  the  fixative  may  be  placed  in  the  bath  to  melt  the  paraffin,  or 
they  may  be  gently  heated  over  a  flame  (with  the  ribbon  side  up),  a  process 
which  must  be  managed  carefully  so  as  not  to  scorch  the  sections.  The 
slide  is  then  placed  upright  in  a  well  of  xylol  (Stender  dishes  are  convenient), 
which  should  not  be  near  the  flame.  The  xylol  will  dissolve  the  melted 
paraffin  in  a  minute  or  so.  The  slide  is  tlien  taken  out  of  the  well  (the  under 
side  wiped  off)  and  either  placed  in  a  well  of  95'v  alcohol  or  a  stream  of 
alcohol  is  run  over  it  from  a  pipette  or  wash  bottle.  The  slide  is  now  ready 
to  be  placed  in  the  staining  wells,  of  which  there  are  various  forms,  but 
Stender  dishes  are  satisfactory. 


208  BOTANICAL  MICROTECHNIQUE 

198.  Bleaching  after  osmic  acid.  Material  fixed  in  clirom-osmo-acetic  acids 
(Flemming's  fluids)  is  always  blackened  by  the  osmic  acid.  This  blackening 
must  be  chiefly  or  wholly  removed  before  staining.  Microtome  sections, 
after  the  solution  of  the  paraffin  with  xylol  and  rinsing  in  95%  alcohol  (Sec. 
197),  are  placed  in  wells  of  5-10%  hydrogen  peroxide  in  70%  alcohol.  The 
bleaching  is  generally  effected  in  an  hour  or  less,  but  may  require  longer. 
Stronger  solutions  of  hydrogen  peroxide  can  be  used  if  necessary,  but  it  is 
safer  to  employ  them  weak.  As  soon  as  the  gray  or  black  tint  is  removed 
the  slide  is  rinsed  in  95%  alcohol  and  is  then  ready  for  the  stain.  Small 
objects  which  are  not  to  be  sectioned  (such  as  filamentous  algse)  are  treated 
in  the  same  manner  in  watch  glasses. 

199.  Staining  on  the  slide.  The  best  stains  for  the  details  of  protoplasm 
are  iron-alum  hsematoxylin,  or  safranin  followed  by  gentian  violet.  Perhaps 
the  most  successful  combination  is  safranin,  gentian  violet,  and  orange  G,  — 
a  combination  known  as  Flemming's  triple  stain,  the  use  of  which  is,  how- 
ever, one  of  the  most  difficult  of  the  staining  methods.  Delafield's  haema- 
toxylin,  and  safranin  followed  by  Delafield's  h?ematoxylin,  are  among  the 
best  general  stains  for  tissues,  and  methyl  green  followed  by  fuchsin  is 
also  good. 

A.  Iron-alum  hcematoxijlin.  This  method  follows  the  same  outline  as  is 
given  in  Sec.  182  for  staining  in  bulk.  The  slide  is  taken  from  95% 
alcohol,  dipped  in  35%,  and  placed  in  iron  alum  (best  used  in  1%  solu- 
tion) for  from  two  to  four  hours ;  it  is  then  rinsed  in  distilled  water  and 
left  in  hsematoxylin  from  four  to  eight  hours  or  over  night.  From  the 
hsematoxylin  it  is  returned  to  the  iron  alum  to  extract  the  stain,  and 
this  process  must  be  watched  with  care,  the  preparation  being  examined 
from  time  to  time  under  the  microscope.  At  the  proper  point  of  extrac- 
tion the  slide  is  placed  in  a  large  disli  of  tap  water,  where  it  must  remain 
for  fifteen  minutes  or  more.  It  is  then  dipped  in  35%  alcohol  (if  desired) 
and  left  two  or  three  minutes  in  a  well  of  95%  alcohol  (it  may  remain 
indefinitely  in  the  95%).  Finally  the  slide  is  taken  from  the  95%  alco- 
hol, drained,  and  some  absolute  alcohol  is  poured  over  the  sections 
from  a  small  bottle  and  rapidly  drained  off,  and  the  slide  placed  as 
soon  as  possible  in  a  well  of  xylol  (clove  oil  should  never  be  used). 
The  preparation  must  remain  in  the  xylol  half  an  hour  or  more,  since 
the  xylol  and  absolute  alcohol  do  not  mix  rapidly,  after  which  it  is 
removed,  the  superfluous  xylol  drained  off,  and  the  sections  mounted 
in  balsam.  Minute  bubbles  on  the  slide  after  having  been  in  xylol 
indicate  that  the  dehydration  has  not  been  perfect,  and  they  must  be 
removed  by  absolute  alcohol  and  the  slide  again  placed  in  xylol. 

B.  Iron-alum  hematoxylin  and  safranin.  The  hsematoxylin  stain  may  be 
extracted  by  iron  alum  until  it  remains  practically  in  the  nucleus  alone. 


STAINING  ON  THE  SLIDE  209 

Then  after  passing  through  tap  water  it  may  be  placed  in  a  solution 
of  safranin  (Sec.  184)  until  the  protoplasm  and  cell  walls  are  slightly 
stained,  after  which  it  is  carried  through  absolute  alcohol  into  xylol. 
DelaHeld's  hoematoxylin.  This  stain  is  excellent  for  tissues,  since  it 
colors  the  cell  walls  sharply,  as  is  not  done  by  iron-alum  haimatoxylin. 
Follow  the  outline  given  in  Sec.  183. 

Safranin,  gentian  violet,  and  orange  G.  It  is  not  necessary  to  use 
the  orange  G  in  this  combination,  known  as  Flemming's  triple  stain,  but 
the  best  results  have  been  obtained  with  it.  The  technique  of  this 
method  of  staining  is  difficult,  but  it  gives  perhaps  the  most  effect- 
ive staining  for  the  study  of  protoplasmic  structure,  especially  during 
nuclear  division.  It  is  impossible  to  give  more  than  a  general  programme 
of  the  method,  since  the  time  limits  necessary  to  obtain  satisfactory 
results  vary  with  different  material  and  must  be  tested  experimentally. 

The  slide  is  transferred  from  95%  alcohol  to  a  well  of  safranin. 
The  alcoholic  solution  mixed  with  an  equal  part  of  water  is  good,  as  is 
also  anilin  safranin  (Sec.  184).  After  remaining  in  safranin  from  four 
to  twenty-four  hours  (over  night  is  generally  convenient),  the  slide  is 
placed  in  50%  alcohol  and  the  stain  extracted  until  it  remains  in  the 
nucleolus  and  chromatin  alone.  Acid  alcohol  (Sec.  184)  may  be  used  to 
extract  the  stain  more  rapidly,  but  it  is  generally  not  necessary. 

The  preparation  is  then  placed  in  a  well  of  gentian  violet.  A  satu- 
rated aqueous  solution  is  good,  or  a  1%  solution  is  generally  strong 
enough.  The  slide  is  left  in  gentian  violet  as  short  a  time  as  possible  to 
obtain  good  results,  and  this  can  only  be  determined  by  trial.  Some- 
times merely  dipping  it  in  the  stain  is  sufficient  ;  other  material  may 
require  a  number  of  seconds,  or  even  minutes.  On  removal  from  gen- 
tian violet  the  slide  is  drained  and  rinsed  in  50%  alcohol,  and  then 
absolute  alcohol  is  poured  over  the  sections,  followed  by  a  few  drops 
of  oil  of  cloves  placed  in  the  center  of  the  preparation.  The  oil  of 
cloves  may  be  replaced  with  cedar  oil  or  xylol  to  avoid  possible  fading 
of  the  stain. 

The  secret  of  success  with  gentian  violet  is  not  to  stain  the  nucleolus 
and  chromatin  so  deeply  that  the  stain  will  not  wash  out.  They  slunild 
be  left  red  and  the  other  protoplasmic  structures  blue.  If  the  nucleolus 
and  chromatin  come  out  blue,  the  slide  has  been  left  too  long  in  gentian 
violet.  In  our  practice  the  best  results  have  come  with  very  short  treat- 
ment in  strong  gentian  violet  (frequently  only  a  dip,  or  a  few  seconds 
timed  by  the  watch),  followed  directly  by  absolute  alcohol.  The  oil  of 
cloves  may  be  depended  upon  to  remove  much  of  the  gentian  violet. 
But,  as  previously  stated,  material  dilTers  very  greatly  in  it«  reaction  to 
gentian  violet,  and  each  subject  recpires  experimentation  and  a  critical 


210  BOTANICAL  MICROTECHNIQUE 

examination  at  various  stages  in  the  process  of  staining,  to  correct  errors. 
The  commonest  mistake  is  to  overstain  with  gentian  violet. 

Should  orange  G  be  brought  into  the  combination,  'the  slide  after  re- 
moval from  gentian  violet  is  rinsed  in  vs^ater  and  placed  in  a  1%  aqueous 
solution  or  a  dilution  of  this  strength.  It  is  left  from  ten  to  thirty  sec- 
onds in  this  stain  and  then  treated  w^ith  absolute  alcohol  and  cleared  in 
oil  of  cloves  as  described  above  for  the  gentian  violet.  The  orange  G, 
if  successfully  used,  will  give  a  grayish  tinge  to  the  cytoplasm,  while 
the  spindle  fibers  (kinoplasm)  will  be  blue  and  the  nucleolus  and  chro- 
matin red.  The  combination,  when  successful,  is  the  most  striking 
stain  known  for  nuclear  figures. 

Slides  should  not  be  destroyed  if  the  results  are  not  up  to  expecta- 
tions. If  the  protoplasm  is  uniformly  blue,  structures  may  still  show 
fairly  well,  and  if  the  stain  is  too  weak,  the  balsam  may  be  removed 
with  xylol  and  the  slide  stained  again.  It  is  not  necessary  to  use 
orange  G,  and  in  our  own  practice  this  stain  is  generally  omitted. 

E.  Safranin  and  BelafieWs  hoematoxylin.  This  combination,  applied  as 
outlined  in  Sec.  185,  is  excellent  for  the  staining  of  tissues,  without 
much  regard  for  the  details  of  protoplasmic  structure,  such  as  nuclear 
figures,  etc. 

F.  Other  stains.  Other  anilin  dyes  besides  safranin  and  gentian  violet  are 
frequently  used  in  staining  on  the  slide.  Fuchsin  (Sec.  186,  A),  methyl 
green  followed  by  fuchsin  (Sec.  186,  B),  and  erythrosin  after  hsematoxy- 
lin,  or  blue  or  green  anihn  stains  (Sec.  186,  C)  give  good  results  for  the 
study  of  tissues.  They  are  especially  satisfactory  for  the  differentiation 
of  structure  in  fibro-vascular  bundles. 


CULTURE  METHODS 


THE  CULTURE  OF  ALGM 

200.  Culture  in  aquaria.  The  most  convenient  forms  of  aquaria  are 
shallow  glass  dishes  eight  to  ten  inches  wide,  battery  jars  six  to  eiglit  inches 
wide,  or  other  large  glass  receptacles.  These  should  be  loosely  covered  with 
pieces  of  heavy  glass  to  keep  out  the  dust,  and  should  not  be  filled  more  than 
two  thirds  full  of  water.  It  is  not  generally  necessary  to  aerate  the  water, 
and  cultures  should  rather  be  left  to  themselves  to  grow  the  forms  with 
which  they  are  stocked,  or  to  develop  whatever  types  may  appear.  It  is  always 
interesting,  and  frequently  surprising,  to  see  what  growths  will  develop  of 
their  own  accord  in  aquaria.  There  should  be  no  metal  in  contact  with  the 
water  of  aquaria,  and  copper  is  especially  poisonous. 

Some  alg?e,  such  as  the  water  net,  Hydrodicti/on,  species  of  (Edogoniinn, 
Coleochocte,  Chara,  Oscillatoria,  and  numerous  one-celled  forms  grow  readily 
in  aquaria.  Other  types  are  more  difficult  to  cultivate,  as  Spirogi/ra  and 
other  pond  scums,  and  it  is  almost  impossible  to  keep  the  red  or  the  brown 
marine  algBe  alive  for  any  length  of  time.  Terrestrial  species  of  Vancheria 
frequently  grow  luxuriantly  over  the  earth  of  the  flowerpots  in  greenhouses. 
Algse  are  more  likely  to  survive  in  aquaria  when  kept  in  the  water  of  the 
ponds  and  ditches  from  which  they  came.  Such  water  may  be  filtered,  and 
the  aquaria  should  be  stocked  with  only  a  small  amount  of  the  algae.  It  is 
not  desirable  to  have  animals  such  as  snails  or  Crustacea  in  the  aquaria,  for 
there  is  almost  sure  to  be  present  a  sufficient  quantity  of  microscopic  forms 
to  preserve  a  balance  of  animal  and  plant  life.  The  aquaria  are  best  placed 
outside  the  room  on  window  ledges,  except  in  freezing  weather,  and  they 
should  have  very  little,  if  any,  direct  sunlight. 

A.   Knop's  solution.    There  are  a  number  of  culture  solutions.    One  of  the 
best  known  is  that  of  Knop,  made  as  follows  : 

potassium  nitrate  1  gram 

potassium  phosphate  1  gram 

magnesium  sulphate  1  gram 

These  three  salts  are  dissolved  in  one  half  liter  of  rain  water  or  fresh 
tap  water,  that  is  tap  water  which  has  not  been  standing  in  metal  pipes. 
To  this  is  added  a  solution  of  4  grams  calcium  nitrate  in  one  half  liter 
of  similar  water.     There  will   be  formed  an  insoluble  precipitate  of 

211 


212  CULTURE  METHODS 

calcium  phosphate  which  is  left  in  the  fluid.  This  makes  a  .7%  solution 
of  the  salts,  which  is  too  strong  for  general  purposes.  It  is  better  diluted 
with  an  equal  quantity  of  water  (making  a  .35%  solution),  or,  for  delicate 
algse,  with  two  liters  of  water  (making  what  is  approximately  a  .2%  solu- 
tion of  the  salts).  Algse  are  placed  directly  in  this  culture  solution, 
and  many  of  them  do  well  in  it. 

B.  Moore's  solution.    Moore  reports  that  the  following  solution  (which  is 

a  modification  of  one  of  Beyerinck's)  is  much  more  satisfactory  than 

that  of  Knop : 

ammonium  nitrate  .5  gram 

potassium  phosphate  .2  gram 

magnesium  sulphate  .2  gram 

calcium  chloride  .1  gram 

iron  sulphate  trace 

These  salts  are  dissolved  in  a  liter  of  water.  For  blue-green  algse  the 
amount  of  ammonium  nitrate  should  be  doubled,  and  1-2%  of  glucose 
may  be  added  with  benefit. 

C.  Cane  sugar.  A  2-4%  solution  of  cane  sugar  is  an  important  fluid,  since 
some  algae  —  as  Vaucheria,  Hydrodictyon,  and  Spirogyra  —  will  gener- 
ally fruit  after  a  few  days  when  transferred  to  it  from  pond  water  or 
culture  solutions  and  exposed  to  bright  light  or  moderate  sunshine. 

201 .  Cultures  on  agar-agar.  Pure  cultures  of  unicellular  algse  may  be  grown 
and  isolated  on  agar-agar  mixed  with  a  nutrient  solution.  Moore  recom- 
mends his  modified  Beyerinck's  solution  (Sec.  200,  B),  with  double  the  amount 
of  ammonium  nitrate  and  2%  of  glucose.  To  a  liter  of  this  solution  (heated  to 
boiling)  5  grams  of  agar  is  added,  and  after  its  liquefaction  the  fluid  is  poured 
into  small  Erlenmeyer  flasks  of  100  cc.  capacity,  or  other  small  dishes  which 
may  be  tightly  covered ;  on  cooling,  the  liquid  will  stiffen  to  a  moist  jelly. 
Pure  cultures  may  be  easily  established  in  such  vessels,  and  if  protected 
from  drying  will  flourish  for  years. 


THE  CULTURE  OF  FUNGI 

202.  Cultures  in  moist  chambers.  Fungi  will  grow  in  abundance  upon  a 
great  variety  of  substances  when  kept  damp  in  moist  chambers.  The  most 
convenient  form  of  a  large  moist  chamber  is  a  rather  low  bell  jar  five  to 
six  inches  high,  set  in  a  dish  of  water.  The  substance  is  placed  on  some  sup- 
port, such  as  a  zinc  rack,  so  that  it  is  raised  above  the  surface  of  the  water, 
the  evaporation  of  which  keeps  the  air  in  the  interior  of  the  bell  jar  moist. 
It  is  well  also  to  ime  the  interior  of  the  bell  jar  with  moist  filter  paper  in  con- 
tact with  the  water  below.    Cultures  upon  large  pieces  of  bread  and  cheese  are 


CULTURE  OF   FUNGI  213 

best  arranged  for  in  this  manner.  Smaller  moist  chambers  may  be  made  by 
placing  filter  paper  above  wet  S2)ha(jniun  on  the  bottom  of  shallow  glass 
dishes,  such  as  crystallizing  dishes,  three  or  more  inches  high,  covered  by  a 
piece  of  glass.  The  substance  to  be  used  as  the  substratum  is  placed  on  the 
filter  paper,  which  is  kept  moist  by  the  Sphagnum.  Such  chambers  are  well 
suited  to  cultures  on  small  pieces  of  fruit  or  other  vegetable  matter,  and  on 
the  dung  of  various  animals.  Cultures  on  horse  dung  are  best  made  in  larger 
dishes  or  under  bell  jars. 

203.  Pure  cultures  on  potato  agar.  Most  saprophytic  fungi  may  be  cul- 
tivated on  potato  agar,  which  is  one  of  the  simplest  and  most  satisfactory 
of  the  culture  media. 

To  make  potato  agar,  pare  two  or  three  medium-sized  potatoes,  cut  into 
thin  slices,  place  in  a  stewpan,  and  cover  with  tap  water.  Allow  the  water  to 
simmer  gently  for  one  half  hour,  or  until  the  potatoes  are  soft  but  not  dis- 
organized. Do  not  let  it  boil.  Strain  the  liquid,  which  should  be  as  clear  as 
possible.  Add  enough  tap  water  to  make  one  half  liter,  and  place  in  a  flask 
with  10  grams  of  agar-agar  cut  up  in  small  pieces.  Heat  the  flask  in  a  steam 
sterilizer  until  the  agar  has  melted  and  mixed  with  the  culture  fluid. 

Clean  about  thirty  test  tubes  (six  laches  long  and  three  fourths  of  an  inch 
across),  rinse,  drain,  and  dry.  Fit  cotton  plugs  of  a  good  quality  into  the 
dry  test  tubes.  They  should  enter  the  tubes  at  least  an  inch  and  project 
somewhat  beyond.  Place  the  tubes  fitted  with  cotton  plugs  in  a  dry-air 
sterilizer  and  expose  to  a  temperature  of  140°  C.  for  an  hour ;  this  will  kill 
all  spores  of  fungi,  including  bacteria,  in  the  tubes  or  on  the  cotton.  The 
tubes  are  best  handled  in  a  receptacle  made  of  heavy  wire  netting,  and  of  a 
size  which  will  slip  into  the  steam  sterilizer. 

Pour  the  melted  potato  agar  into  the  test  tubes  by  means  of  a  funnel, 
removing  the  cotton  plug  carefully  and  holding  between  the  fingers  while  fill- 
ing each.  The  tubes  should  be  filled  up  about  one  and  one-half  inches  from  the 
bottom.  It  is  very  important  that  no  agar  become  smeared  around  the  top 
of  the  test  tube  where  the  plug  is  inserted.  The  filled  tubes,  carefully  pluggeil, 
are  now  sterilized  twice  a  day  (morning  and  night)  on  three  successive  days 
in  the  steam  sterilizer  for  an  hour  each  time.  This  is  necessary  to  render  the 
+.ubes  free  from  bacteria,  for  the  spores  of  bacteria  are  not  generally  killed 
by  the  temperature  of  100°  C,  but  they  germinate  quickly  in  the  potato 
agar,  and  the  vegetative  bacteria  produced  by  them  are  then  killed  by  that 
temperature. 

After  the  sterilization  of  the  third  day  the  tubes  are  taken  out  and  laid  on 
a  table  inclined  against  a  board  so  that  the  surface  of  the  hot  fluid  agar  runs 
three  or  four  inches  up  the  sides  of  the  tubes.  As  they  cool,  the  agar  stiffens 
in  this  position,  forming  a  long,  slanting  surface  in  each  tube,  which  is  now 
ready  for  inoculation. 


214  CULTURE  METHODS 

Transfers  of  spores  are  made  to  the  tubes  by  means  of  a  piece  of  stiff 
platinum  wire  about  two  inches  long,  set  in  the  end  of  a  glass  rod  when 
melted  in  a  flame.  The  lower  end  of  the  rod  and  the  wire  are  sterilized  in  a 
flame  and  the  point  of  the  wire  is  touched  to  a  single  spore-bearing  hypha 
in  a  culture.  The  cotton  plug  is  then  carefully  removed  from  a  tube  and 
held  between  the  fingers  while  the  point  of  the  wire  is  drawn  over  the  sur- 
face of  the  agar.  It  is  best  that  the  tube  be  held  inverted  while  being  inoc- 
ulated so  that  dust  may  not  enter.  The  plug  is  replaced  quickly  and  the 
inoculated  tube  is  laid  aside  to  await  developments.  If  but  a  single  spore- 
bearing  filament  has  been  touched,  the  culture  will  probably  be  pure.  Should 
an  impure  culture  develop,  transfers  may  generally  be  made  from  it  to 
another  tube.  Tubes  with  cultures  may  be  prevented  from  drying  out  too 
rapidly  by  cutting  off  the  tops  of  the  cotton  plugs  and  coating  the  ends  of  the 
tubes  with  paraSin. 

Potato  agar  may  be  poured  into  Petri  dishes  and  sterilized  in  the  same 
manner  as  the  test  tubes.  Such  dishes  are  excellent  for  studies  upon  the 
bacteria  as  outlined  in  Sec.  100. 

204.  Hanging-drop  cultures.  These  are  used  for  the  study  of  germinating 
spores,  pollen  grains,  and  other  subjects.  The  spores  are  placed  in  a  drop 
of  the  culture  fluid  on  a  cover  glass,  which  is  then  arranged  so  that  the  drop 
hangs  down  from  the  lower  side  in  a  small  moist  chamber  on  a  slide.  The 
chamber  may  be  made  of  a  ring  of  glass  cemented  on  the  slide  with  wax  or 
gold  size  (Van  Tieghem  cell),  over  which  the  cover  glass  fits  and  is  sealed 
with  vaseline.  A  little  distilled  water  in  the  bottom  of  the  chamber  will  save 
some  evaporation  from  the  drop  of  the  culture  fluid, 

A  more  temporary  but  also  effective  chamber  may  be  made  by  cutting  a 
square  hole  about  one  half  inch  in  diameter  in  the  center  of  a  piece  of  card- 
board one  inch  wide,  one  and  one-half  inches  long,  and  one  eighth  of  an 
inch  or  more  thick.  The  cardboard  is  boiled  and  pressed  closely  on  the  slide. 
The  culture  drop  is  then  placed  in  the  center  of  a  cover  glass  an  inch  square 
or  slightly  smaller.  This  is  inverted  over  the  hole  in  the  cardboard  so  that  the 
culture  drop  hangs  down  in  the  center  and  the  cover  glass  is  then  pressed 
closely  against  its  wet  surface.  Water  is  added  from  time  to  time  to  the 
edge  of  the  cardboard  to  keep  it  moist,  and  the  slide  when  not  being  studied 
may  be  placed  in  a  moist  chamber,  which  will  hinder  the  cardboard  from 
drying  rapidly. 

The  culture  fluids  vary  with  the  subject.  Boiled  decoctions  of  horse  dung 
are  good  for  the  germination  of  many  fungal  spores.  Decoctions  of  decayed 
wood  are  used  for  the  spores  of  slime  molds.  Solutions  of  sugar  (3-30%  in 
tap  water)  are  employed  in  the  germination  of  pollen  grains  (see  Experiment 
XLII)  ;  1.5%  of  gelatin  may  sometimes  be  added  to  advantage  to  the  sugar 
solutions.    Spores  of  mosses  and  ferns  germinate  readily  in  sweetened  water. 


CULTURE   OF   LIVERWORTS   AND   MOSSES  215 

THE  CULTURE  OF  LIVERWORTS  AND  MOSSES 

205.  The  culture  of  liverworts.  Aciuatic  liverworts,  such  as  liicciocarpus 
natans  and  some  species  of  Riccia,  will  sometimes  grow  fairly  well  in  large 
glass  aquaria,  but  they  must  have  pure  air  and  considerable  water.  They  will 
do  much  better  in  tanks  or  cement  basins  in  greenhouses.  The  terrestrial 
liverworts,  such  as  MarcAan^/a,  Lunid<irl(i,  Comctphalm,  and  related  types, 
grow  readily  on  damp  soil  in  greenhouses  or  in  large  vessels  covered  with 
glass.  These  forms  and  various  mosses  are  frequently  present  in  ill-kept 
greenhouses.  They  will  not  do  well  in  very  bright  light,  preferring  shaded 
situations,  and  must  have  abundant  moisture  in  the  earth.  If  convenient, 
it  is  well  to  cultivate  them  on  soil  from  their  habitats. 

206.  The  culture  of  protonemata.  Moss  spores  germinate  readily,  and  il  is 
not  difficult  to  obtain  luxuriant  cultures  of  protonemata.  These  frequently 
appear  over  the  surface  of  earth  in  flowerpots  in  greenhouses,  and  then 
somewhat  resemble  the  more  common  growths  of  Vaiirheria.  Cultures  of 
the  spores  are  conveniently  made  in  bulb  pots  or  other  wide  pots  set  in  sau- 
cers of  water.  After  filling  the  pot  with  earth  to  an  inch  from  the  top,  it  is 
well  to  heat  it  for  two  or  three  hours  in  a  steam  sterilizer  to  kiU  fungi  which 
might  be  troublesome,  but  this  is  not  absolutely  necessary. 

The  spores  of  many  of  the  common  mosses  of  the  fields  will  grow  readily, 
but  species  of  Funaria  are  especially  satisfactory.  The  spore  cases  may  be 
crushed  over  a  sheet  of  paper  to  remove  the  spores,  which  are  thengently 
blown  over  the  surface  of  the  earth.  The  top  of  the  pot  is  covered  with  a 
piece  of  glass  and  the  culture  is  watered  from  the  saucer  below.  The  earth 
should  be  merely  moist,  not  wet,  for  too  much  moisture  may  result  in  the 
death  of  the  culture  by  "damping  off"  from  the  growth  of  fungi.  The 
earth  will  shortly  become  covered  with  a  growth  of  green  filaments.  After 
two  or  three  weeks,  buds  will  be  developed,  followed  by  the  appearance  of 
the  leafy  moss  plants.  ■ 

207.  Moss  cultures.  A  thick  growth  of  leafy  moss  plants  generally  arises 
from  the  protonemata  as  described  above.  These  plants  will  in  time  develop 
sexual  organs,  the  antheridial  plants  being  easily  distinguished  by  the  rosette 
of  expanded  leaves  around  the  yellow  or  orange-colored  clusters  of  anther- 
idia.  The  archegonia  will  not  be  fertilized  if  the  culture  is  watered  entirely 
from  the  saucer  below.  When  sporophytes  are  desired  the  culture  must  be 
flooded  with  water,  first  closing  with  a  cork  the  opening  in  the  pot  below. 
It  should  remain  flooded  for  an  hour  or  more,  aftep  which  the  water  may 
be  allowed  to  run  off.  All  ripe  archegonia  and  antheridia  will  have  opened, 
and  the  eggs,  having  been  fertilized,  will  develop  sporophytes.  By  succes- 
sively flooding  the  culture  at  intervals,  sporophytes  in  varioua  stages  of 
development  may  be  obtained. 


216  CULTURE  METHODS 

THE  CULTURE  OF  FERNS 

208.  The  culture  of  fern  prothallia.  Fern  prothallia  may  be  cultivated  even 
more  easily  than  moss  protonemata.  The  method  is  essentially  the  same. 
The  spores  of  common  greenhouse  ferns  will  germinate  readily,  but  the  pro- 
thallia of  some  present  abnormalities  due  to  apogamy  {Principles,  Sec.  311), 
so  it  is  better  to  sow  the  spores  of  some  of  the  wild  ferns,  such  as  Pteris 
aquilina,  species  of  Onoclea,  Aspidium,  Polypodium,  etc.  Such  spores  gen- 
erally retain  their  vitality  for  a  year  or  more.  The  spores  of  Osmunda,  on 
the  contrary,  and  also  those  of  Equisetum  live  only  a  few  days  and  must  be 
sown  at  once  at  maturity,  but  then  give  very  luxuriant  cultures. 

The  spores,  crushed  out  of  their  sporangia  on  a  piece  of  paper,  are  blown 
over  the  surface  of  earth  in  bulb  pots  or  shallow  dishes.  These  are  covered 
with  glass  and  the  pot  is  set  in  a  saucer  and  watered  from  below.  The  earth 
in  the  pot  may  be  sterilized  with  advantage  (Sec.  206).  The  culture  should 
not  be  kept  too  moist,  for  there  is  danger  of  the  prothallia  damping  off. 
Prothallia  will  begin  to  develop  antheridia  in  three  or  four  weeks  and  will 
be  full-grown  in  six  weeks.  Care  should  be  taken  not  to  sow  the  spores  too 
thickly,  at  least  in  portions  of  the  dish,  for  crowded  growths  of  prothallia 
remain  dwarf  and  only  develop  antheridia. 

Growths  of  young  fern  sporophytes  are  obtained  by  flooding  a  culture  of 
mature  fern  prothallia  for  an  hour  or  more,  closing  the  bottom  of  the  pot  tem- 
porarily as  described  in  Sec.  207.  In  a  few  weeks  the  first  leaves  of  the  young 
fern  plants  will  appear,  growing  up  in  the  notch  of  the  large  fern  prothallia. 

209.  Water  ferns.  The  floating  water  ferns  Salvinia  and  Azolla,  like  the 
floating  liverworts  (Sec.  205),  will  grow  in  glass  vessels  if  they  have  pure  air 
and  plenty  of  water,  but  they  do  much  better  in  large  tanks  or  cement  basins 
in  greenhouses.  Marsilia  is  hardy  and  grows  well  in  tanks  or  basins.  Sal- 
vinia and  Azolla  may  be  kept  thus  over  winter,  and  in  the  spring,  when 
placed  in  ponds  out  of  doors,  will  generally  do  well.  Marsilia  is  easily  intro- 
duced into  ponds,  where  it  forms  thick  growths  in  shallow  water.  Salvinia 
is  not  uncommon  under  cultivation  in  water-lily  ponds  of  city  parks. 


THE  CULTURE  OF  SEED  PLANTS 

210.  Directions  for  the  culture  of  seed  plants.  It  is  hardly  worth  while  to 
give  an  account  of  the  manner  in  which  such  seed  plants  as  are  needed  for 
studies  and  demonstrations  are  best  cultivated.  The  advice  of  a  competent 
florist  will  be  found  more  helpful  than  any  set  of  printed  directions.  Das 
PJianzenmaterial  fur  den  botanischen  Unterricht,  by  Dr.  P.  Esser,  I.  Teil, 
Cologne,  1903,  gives  much  useful  information.    Its  price  is  Marks  3.20. 


MATERIAL,  APPARATUS,  AND  SUPPLIES 


LISTS  OF  PREPAEATIONS  FOR  THE  MICROSCOPE 

211.  Slides  of  value  in  studies  on  the  plant  cell. 

Spirogyra.  To  show  the  nucleus  :  filaments  fixed  in  weak  chrom-acetic 
acid  (Sec.  172,  A),  stained  in  iron-alum  hsematoxylin  (Sec.  182),  mounted  in 
glycerin  (Sec.  188)  ;  or  stained  in  Magdala  red  and  anilin  blue  and  mounted 
in  Venetian  turpentine  (Chamberlain,  Methods  of  Histology,  p.  81,  1905). 

Root  tip  of  onion  or  hyacinth.  For  the  study  of  cell  and  nuclear  division  : 
fixed  in  medium  chrom-acetic  (Sec.  172,  B),  or  weak  Flemming  (Sec.  173,  A), 
sectioned  in  paraflBn  from  five  to  seven  micromillimeters  thick,  stained  with 
safranin  and  gentian  violet  (Sec.  199,  D). 

Pollen  mother  cells  of  the  lily  or  related  types.  Also  excellent  subjects 
for  the  study  of  cell  and  nuclear  division  (see  Lilium  in  next  section). 

212.  Slides  of  value  in  type  studies.  The  following  list  of  preparations  is 
merely  suggestive ;  many  other  subjects  may  be  added.  It  is  a  mistake  to 
suppose  that  permanent  preparations  are  necessary  for  type  studies.  They 
will,  however,  at  times  be  of  great  assistance.  The  accumulation  of  class 
preparations  requires  time  and  patience  and  their  proper  use  demands 
judgment.  There  is  much  danger  in  giving  slides  to  students  before  they  are 
prepared  to  understand  from  studies  on  living  or  preserved  material  the 
topography  and  significance  of  the  structures  shown  in  the  preparations. 

Volvox.  Whole  colonies,  safranin  or  iron-alum  luiMnatoxylin,  carried  with 
care  into  balsam  (Sec.  187),  the  cover  glass  supported  by  two  strips  of  paper 
to  prevent  crushing. 

Ulothrix,  or  other  alga,  forming  zoospores.  Iron-alum  hrematoxylin  and 
safranin  (Sec.  182),  carried  with  care  into  balsam. 

(Edogonium.  Iron-alum  hsematoxylin  and  safranin,  glycerin,  or  carried 
with  care  into  balsam. 

Coleochmte.    Fruiting  thallus,  Delafield's  hi^matoxylin  (Sec.  183),  balsam. 

Fucus.  Parafl&n  sections  of  oiigonial  conceptacles  to  show  histological  de- 
tails, safranin  and  gentian  violet,  orD.'s  ha-matoxylin. 

Sporodinia  or  Rhizopus.  Zygospores  with  mycelium  slightly  stained  with 
D.'s  haematoxylin,  glycerin,  or  balsam. 

Albugo.  Paraffin  sections  of  (1)  blisters,  D.'s  haematoxylin  ;  (2)  tissue  with 
oogonia,  safranin  and  gentian  violet. 

217 


218  MATERIAL,  APPARATUS,  AND  SUPPLIES 

Peziza  or  other  cup  fungus.  Paraffin  sections  of  fruiting  surface,  safranin 
and  gentian  violet. 

Puccinia.  Paraffin  sections  (1)  across  sori  of  teleutospores  and  uredo- 
spores  ;  (2)  cluster  cup  on  barberry,  D.'s  h?ematoxylin. 

Coprinus  or  other  gill  fungus.  Paraffin  sections  of  gills,  cut  rather  thick, 
showing  basidia  with  spores,  D.'s  hsematoxylin. 

Marchantia.  Paraffin  sections  (1)  of  thallus,  safranin  and  D.'s  hsematox- 
ylin  (Sec.  185)  ;  (2)  antheridial  receptacles,  D.'s  hsematoxylin  ;  (3)  arche-. 
gonial  receptacles  for  archegonia  and  sporophytes,  safranin  and  D.'s 
hsematoxylin. 

Porella.  Paraffin  lengthwise  sections  (1)  of  antheridial  branches,  D.'s 
hsematoxylin  ;  (2)  archegonial  branches  for  sporophytes,  safranin  and  D.'s 
hsematoxylin. 

Anthoceros.  Paraffin  lengthwise  sections  of  medium-sized  sporophytes 
attached  to  small  pieces  of  the  gametophytes,  safranin  and  D.'s  hsematoxylin. 

Funaria,  Mnium,  or  Atrichum.  Paraffin  sections  (1)  of  the  tips  of  anther- 
idial and  archegonial  plants ;  (2)  medium-sized  spore  cases  for  spore-bearing 
tissue,  D.'s  haematoxylin. 

Webbera.  Protonema,  common  in  greenhouses,  frequently  forms  buds 
in  great  numbers,  safranin,  carried  with  care  into  balsam. 

Aspidium.    Paraffin  sections  of  sorus,  D.'s  hsematoxylin. 

Pteris  aquilina.  (1)  Cross  and  lengthwise  sections  of  rhizome  (Sec.  194) 
mounted  on  the  same  slide,  safranin  and  D.'s  hsematoxylin. 

Pteris  or  other  fern.  Paraffin  lengthwise  sections  of  (1)  root  tip;  (2)  large 
prothallia  to  show  archegonia  and  occasional  developing  sporophytes,  safranin 
and  D.'s  haematoxylin. 

Pinus.  (1)  Cross  sections  of  needle,  safranin  and  D.'s  hsematoxylin ; 
(2)  Sections  of  wood,  cross,  radial,  and  tangential,  mounted  on  the  same 
slide,  safranin  and  D.'s  haematoxylin,  or  methyl  green  and  fuchsin  (Sec. 
186,  B)  ;  (3)  paraffin  lengthwise  sections  of  ovules  from  a  year-old  cone, 
safranin  and  gentian  violet  or  safranin  and  D.'s  haematoxylin. 

Lilium  or  related  types.  (1)  Paraffin  cross  and  lengthwise  sections  of 
anthers,  showing  pollen  mother  cells  in  stages  of  nuclear  and  cell  division, 
also  sections  of  mature  anthers  ;  (2)  paraffin  cross  sections  of  ovule  cases  of 
various  ages  to  show  the  development  and  structure  of  the  embryo  sac  and 
ovule  ;  (3)  double  fertilization  in  embryo  sac  ;  (4)  development  of  embryo 
and  endosperm  ;  all  stained  with  safranin  and  gentian  violet,  or  safranin, 
gentian  violet,  and  orange  G  (Sec.  199,  D). 

Sambucus.  Paraffin  cross  sections  of  mature  anthers  to  show  gameto- 
phyte  nuclei  in  the  pollen  grain,  safranin  and  gentian  violet. 

Capsella.  (1)  Paraffin  lengthwise  sections  of  tip  of  growing  raceme  to 
show  stages  in  the  development  of  the  flowers,  D.  's  haematoxylin  ;  (2)  paraffin 


LISTS  OF   PlIKPAUATIOXS  219 

lengthwise  sections  of  ovules  after  fertilization,  sliowin^  embryo  in  embryo 
sac,  safranin  and  D.'s  luomatoxylin. 

213.  Slides  of  value  in  histological  studies  on  the  seed  plants. 

ROOTS 

Corn  root  tip.  Lengthwise  section,  showing  plerome,  periblem,  and  dor- 
matogen,  safranin  and  Delafield's  haematoxylin. 

Tradescantia  root  tip.  Lengthwise  section,  showing  general  root  struc- 
ture and  nuclear  division,  safranin  and  gentian  violet. 

Smilax  root.  Cross  section,  showing  cortex,  endodermis,  and  radial 
bundles,  safranin  and  D.'s  haematoxylin. 

STEMS 

Hippuris  shoot.  Lengthwise  section  of  stem  apex,  showing  meristem, 
origin  of  lateral  shoots  and  leaves,  safranin  and  D.'s  hiematoxylin. 

Indian  corn  stem.  Lengthwise  section,  showing  sieve  tubes,  companion 
cells,  annular  tracheids  and  sclerenchyma,  safranin  and  D.'s  hieniatoxylin. 

Pumpkin  stem.  Lengthwise  section,. showing  sieve  tubes  and  companion 
cells  and  vessels,  safranin  and  D.'s  hematoxylin. 

Menispermum  stem.  Cross  section,  showing  separate  bundles  of  a  climbing 
stem  with  large  vessels  for  conducting  water,  safranin  and  D.'s  luematoxyHn. 

Brasenia  stem.  Cross  section,  showing  typical  structure  of  an  aquatic 
stem  with  large  air  cavities  and  scanty  vascular  system,  D.'s  h;ematoxylin. 

Dodder  on  golden-rod  stem.  Cross  section,  showing  penetration  of  stem 
tissues  by  haustoria,  safranin  and  D.  's  haematoxylin. 

LEAVES 

Cycas  revoluta.  Cross  section,  extremely  xerophytic  leaf  structure  witli 
thick  cuticle,  highly  developed  palisades,  and  depressed  stomata,  safranin 
and  D.'s  haematoxylin. 

Peperomia.  Cross  section,  typical  of  water  storage  in  the  leaf  outside  of 
the  photosynthetic  tissue,  D.'s  hiematoxylin. 

Silphium  laciniatum.  Cross  section,  vertical  k^af  with  a  palisade  layer 
near  each  surface,  D.'s  hematoxylin. 

Potamogetni.  Cross  section,  submerged  leaf  with  thin  epidermis,  no  sto- 
mata nor  palisades,  large  air  cavities  and  scanty  vascular  system,  D.'s 
haematoxylin. 

Water  buttercup.  Cross  sections  (1)  of  aerial  leaf  ;  (2)  submerged  leaf, 
D.'s  hgematoxylin. 


220  MATERIAL,  APPARATUS,  AND  SUPPLIES 

SUGGESTIONS  "ON    MATERIAL    FOE,   THE  STUDY  OF 
PLANT  HISTOLOGY 

214.  Histological  material  of  the  seed  plants. 

Air  passages.  Eootstock  of  sweet  flag  {Acorus);  stem  of  Jujicus,  Myrio- 
phyllu7n,  Scirjyus;   leafstalks  and  flower  stalks  of  pond  lily  and  of  Nyinphoia. 

Aleurone  grains.    Seeds  of  almond,  Brazil  nut,  castor  bean,  and  nutmeg. 

Bast  fibers.  Stem  of  flax,  of  hemp,  of  linden  (young  twig)  ;  leaf  of  Cariu- 
dovica,  esparto  grass,  palm,  pineapple. 

Bundles,  closed.  Stem  of  asparagus,  corn,  green  brier  (Smilax)  ;  flower 
stalks  or  leaves  of  Yucca  filainentosa ;  petioles  of  fan  palm  leaves  (cut  if 
necessary  from  the  handle  of  a  palm-leaf  fan). 

Bundles,  open.  Young  stems  of  Aristolochia,  Begonia,  Clematis,  evening 
primrose,  Menispermmn ;  stems  of  sunflowers  or  other  large  composites. 

Cambium.    See  Bundles,  open. 

Cambium,  cork  (phellogen).  Young  twigs  of  ^6H^iZo?i  (greenhouse  species) 
and  of  elder. 

Central  cylinder  of  root.  Roots  from  bulb  of  hyacinth  or  onion  ;  roots  of 
Acorus,  Actcea,  Smilax,  Veratrum. 

Chlorophyll  bodies.  Best  seen  in  leaves  of  moss,  as  Funaria  or  Mnium,  or 
in  fern  prothallia  ;  thin  sections  of  any  green  leaves  or  upper  epidermis  torn 
off,  with  the  tops  of  the  palisade  cells  attached  ;  large  and  distinct  in  leaves 
or  bracts  of  pineapple. 

'  Chromatophores  or  chromoplasts.  Surface  sections  from  sepals  of  Tro- 
pceolum,  pulp  of  fruit  of  Cratoegus,  asparagus,  or  rose,  root  of  carrot ;  many 
algse,  such  as  Spirogyra,  Ulothrlx,  desmids,  diatoms,  Ectocarpus,  Nema- 
lion,  etc. 

Collenchyma.  Young  stems  of  Aristolochia  Sipho ;  stems  of  begonias. 
Salvia,  and  most  Umbelliferce. 

Cork.  Young  twig^  of  Ailanthus,  sweet  gum  (Liquidambar),  cherry, 
currant,  Laburnum  mdg are,  Ewnymus  alatus ;  ordinary  bottle  corks  (from 
Quercus  Suber)  ;  cortex  of  potato  tuber. 

Cuticle.  Leaves  of  Agave,  Aloe,  Cycas  revoluta,  Ficus  elastica.  Yucca  fila- 
mentosa. 

Embryo  sac.    Lily,  buttercup,  and  their  allies. 

Epidermis.  See  under  Cuticle.  Also  thin  and  easily  peeled  epidermis  of 
iris,  lily,  hyacinth. 

Fertilization  and  development  of  embryo.  Young  fruit  of  Capsella,  Mono- 
tropa,  Pyrola,  Veronica,  lily,  buttercup. 

Growing  point.  Tip  of  stem  of  Myriophyllum  or  Hippuris  ;  buds  of  lilac, 
Crataegus,  Viburnum. 


MATERIAL  FOR  STUDY  OF  PLANT  HISTOLOGY     221 

Hairs  and  scales.  Glandular  hairs,  "  geraniums,''  most  LabiaUr,  sundew, 
tomato  ;  ordinary  unbranched  hairs,  leaves  and  stems  of  most  Borraffinareai, 
Gnaphallum,  seeds  of  cotton  ;  scale-like  hairs,  leaves  of  Elaiagnus,  olive, 
Shepherdia;  star-shaped  hairs,  leaves  of  Matthiola;  stinging  hairs,  stem  of 
nettle  ;  T-shaped  hairs,  leaves  and  stems  of  Artemisias;  branched  hairs  of 
mullein. 

Laticiferous  tissue.  Root  of  chicory,  of  dandelion  ;  stem  of  Eujihorhia 
splendens,  of  lettuce  ;  bract  of  Ficus  elastica. 

Leaf  structure.  Hydrophytic :  Elodea,  Potaniogcton,  submerged  leaves 
of  Sagittaria;  mesophytic :  most  deciduous  trees  and  shrubs;  xero[)liytic : 
see  under  Cuticle, — also  bearberry,  crowberry,  Eluiagnus,  holly,  oleander, 
mistletoe,  olive. 

Lenticels.    Young  twigs  of  birch,  cherry,  elder,  and  sumac. 

Leucoplasts.  Pseudo-bulbs  of  Phajus  grandlfolius,  rootstocks  of  Iris  gcr- 
manica. 

Nuclear  division  (mitosis).  Pollen  mother  cells  of  lily  and  its  allies  ;  cells 
of  root  tip  of  onion  or  hyacinth. 

Nuclei.  Epidermal  cells  of  many  leaves  ;  growing  points  of  roots  or 
stems ;  hairs  of  roots,  stamen  hairs  of  Tradescantia,  hairs  of  stem  of  cucum- 
ber ;  internodes  of  Tradescantia ;  bulb  scale  of  onion;  pollen  mother  cell.s 
of  lily  and  its  allies. 

Oil  and  resin  glands.  Aments  of  the  hop  ;  hairs  and  emergences  on  leaves 
of  any  aromatic  Labiatm  ;  leaves  of  Eucalyptus  globulus,  of  L'uta ;  rind  of 
lemon  or  orange. 

Oil  as  reserve  material.  Oily  seeds,  as  almonds,  Brazil  nuts,  cacao  seeds, 
castor  beans,  peanuts,  squash  seeds,  sunflower  seeds. 

Pcdisade  cells.  Leaves  of  beech,  Cycas,  English  ivy,  Ficus  elastica,  holly, 
Japan  quince,  mistletoe,  oleander,  poplar,  privet,  willow,  yucca. 

Pollen  tubes.  Pollen  of  snowdrop  (Leucojum),  sweet  pea,  Tropaoluui, 
tulip. 

Root,  dicotyledonous.  Beans  and  other  Leguminosa',  Composita\  gi-apevino. 
primrose,  Ranuncidus ;  very  young  roots  of  most  hardwood  shrubs  and 
trees. 

Boot,  monocotyledonous.  See  Central  cylinder  of  root.  Also  asparagus. 
Aspidistra,  corn  and  other  large  grasses.  Iris,  sedges,  Stnilax. 

Rootcap.  Monocotyledonous:  corn  and  other  grasses,  Iris:  dicotyledo- 
nous :  bean,  pea,  sunflower,  Tradescantia  grown  in  water. 

Root  hairs.  Most  roots  of  very  young  seedlings  from  seeds  sprouted  on 
wet  paper  in  a  slightly  damp  atmosphere,  Tradrsrantia  grown  in  water. 

Sclerenchy  ma  fibers.    See  Bast  fibers  and  Woodfbcrs. 
•    Secondary  thickening.    Twigs  two  years  old  and  more  of  coniferous  and 
of  hardwood  trees. 


222  MATERIAL,  APPARATUS,  AND  SUPPLIES 

Seeds.  With  endosperm  :  buckwheat,  castor  bean,  four-o'clock,  all  grasses, 
morning-glory,  honey  locust ;  without  endosperm  i :  all  Cucurhitacece,  most 
Leguniinosoe,  many  Eosaceoe. 

Sieve  tubes.    Stems  of  CucurbitaceoB,  young  stems  of  grapevine. 

Starch.  Rootstocks  of  arrowroot  (Maranta),  of  Canna ;  seeds  of  beans, 
buckwheat,  corn,  oats,  rice,  wheat ;  stems  of  Euphorbias;  tubers  of  potato. 

Stem,  dicotyledonous.  See  Bundles,  open.  Very  young  twigs  of  most  hard- 
wood shrubs  and  trees. 

Stem,  monocotyledonous.  See  Bundles,  closed.  Rootstocks  of  grasses  and 
sedges  ;  stem  of  bamboo  and  of  rattan. 

Stomata.  Leaves  of  Aloe,  of  CrassulacecE,  Cycas  revoluta,  Ficus  clastica, 
Iris,  Liliaceoe,  oleander. 

Stone  cells.    Allspice  fruit,  clove  flower  stalk,  oak  bark,  pear-fruit  stalk. 

Tracheids.    Wood  of  any  coniferous  shrub  or  tree. 

Vessels.  Leaf  of  banana ;  peduncle  of  banana,  of  yucca ;  root  of 
Acorus,  of  Iris;  stem  of  corn,  evening  primrose,  grapevine,  rattan,  Ricinus, 
sunflower. 

Water-storage  system.  Leaves  of  Agave,  Aloe,  Ficus  elastica,  Mesembryan- 
thaceoi,  Peperomia ;  stems  of  Cactacew. 

Wood  fibers.  Fibrous  hard  wood,  as  alder,  birch,  hickory,  linden,  locust, 
magnolia,  poplar  (Populus). 

Wood  parenchyma.  Wood  of  apple,  bladder  nut,  hawthorn,  linden,  pear, 
red  cedar,  rose. 

References.  Strasburger-Hillhouse,  6 ;  Strasburger,  Noll,  Schenck, 
Karsten,  1  ;    Tschirch,  74. 

APPAEATUS  FOE  THE  LABOEATOEY 

215.  Apparatus.  The  stocking  of  a  laboratory  with  apparatus  is  a  matter 
of  time  and  experience,  depending  upon  the  character  of  the  work  given. 
The  following  list  is  therefore  merely  suggestive  : 

Aquarium  jars.    Large  battery  jars  or  museum  jars  are  also  good. 

Balances,  large,  capacity  yL  gram  to  2  kilograms,  with  weights. 

Balances,  small,  capacity  1  milligram  to  100  grams,  with  weights. 

Battery  jars,  glass,  quarts  and  gallons. 

Bell  jars  from  five  to  six  inches  high,  and  one  or  more  tall  ones. 

Blotting  paper. 

Bottles,  dropping. 

Bottles,  glass  stoppered,  assorted. 

Bottles,  ordinary  wide  mouthed,  assorted. 

Boxes,  small,  wooden,  for  germination  experiments. 

1  I.e.  with  the  reserve-material  practically  all  contained  in  the  embryo,  even 
if  traces  of  endosperm  remain. 


APPARATUS  FOR  THE  LABORATORY      223 

Camera  lucida. 

Chemical  thermometers,  registering  100"  C.  and  above. 

Clinostat. 

Clock  glasses. 

Corks. 

Crystallizing  dishes. 

Culture  jars,  large  and  small  flat  glass  dishes. 

Dishes,  ordinary  plates  and  saucers. 

Evaporating  dishes. 

Eyepiece  micrometer. 

Flasks. 

Flowerpots,  ordinary,  and  bulb  pots,  with  saucers. 

Funnels,  glass,  assorted  sizes. 

Glass  growing  case  (see  Wardian  case). 

Graduated  cylinders,  10,  100,  500  cc. 

Hones,  one  rough  for  scalpels,  one  Belgian  or  carborundum  for  microtome 

knives. 
Imbedding  oven. 
Lead,  thin  sheet. 

Mason  butter  jars  for  preserved  material. 
Microtomes. 

Museum  jars,  very  useful  but  expensive. 
Petri  dishes. 

Pipettes  (medicine  droppers). 
Printing  frames,  photographic. 

Printing  paper,  ordinary  photographic  and  for  blue  prints. 
Razor  strops. 
Retort  stands. 
Sand. 
Sawdust. 

Stage  micrometer. 
Stender  dishes. 
Sterilizer,  steam. 
Test  tubes. 
Thermostat. 
Thistle  tubes. 
Tools,  such  as  hammer,  saw,  file,  screw-driver,  pliers,  monkey  wrench, 

cork  borers,  etc. 
Tubing,  glass  assorted  and  also  rubber. 
Tumblers. 

Wardian  case  (glass  growing  case),  Ganong,  7,  p.  82. 
Wash  bottles. 
Watch  glasses,  solid. 


224  MATERIAL,  APPARATUS,  AND   SUPPLIES 

CHEMICALS  FOR  THE  LABORATOEY 

216.  The  supply  of  necessary  chemicals  in  a  laboratory  will  depend  upon 
the  character  of  the  work.   This  list  is  therefore  merely  suggestive. 

Acids,  commercial  acetic,  glacial  acetic,  chromic,  hydrochloric,  nitric, 
osmic,  sulphuric. 

Alcohol,  commercial  and  denatured. 

Alcohol,  absolute. 

Ammonia. 

Ammonia  sulphate  of  iron  (iron  alum). 

Benzine. 

Calcium  nitrate. 

Calcium  oxide  (quicklime). 

Calcium  sulphate  (plaster  of  Paris). 

Canada  balsam. 

Chloroform. 

Chlorzinc  iodine  (see  Sec.  169). 

Ether. 

Fehling's  solution  (see  Sec.  170). 

Ferric  chloride. 

Formalin. 

Glycerin.  » 

Grafting  wax. 

Hydrogen  peroxide. 

Iodine. 

Magnesium  sulphate. 

Mercury. 

Millon's  reagent  (see  Sec.  170). 

Oil  of  cloves,  cedar  oil,  olive  oil. 

Parafi&n,  hard  and  soft. 

Potassium  chloride. 

Potassium  hydroxide  (caustic  potash),  5%  and  15%  solutions  (see  Sec.  169). 

Potassium  permanganate. 

Potassium  phosphate,  acid. 

Sodium  chloride  (common  table  salt  and  also  c.p.). 

Stains,  acid  fuchsin,  eosin,  erythrosin,  gentian  violet,  hsematoxylin, 
iodine,  methyl  green,  orange  G,  phloroglucin,  safranin  (directions  for 
making  up  these  stains  are  given  in  Sees.  169,  170,  181-186). 

Sugar,  cane. 

Vaseline. 

Water,  distilled. 

Xylol. 


DEALERS  IN  SUPPLIES  226 


DEALERS  m  MATERIAL,  APPARATUS,  AND  SUPl»LIi:S 

217.  Material  and  slides.  Plant  material,  both  preBerved  and  dried,  and 
prepared  slides  for  the  microscope  are  offered  by  the  following  dealers,  from 
whom  price  lists  may  be  obtained. 

A.  The  Plant  Study  Company,  Cambridge,  Mass.  Living  material,  cspo- 
cially  algcB  and  aquarium  plants.  Accurately  named  fungi  of  every 
description.  Phanerogamic  and  other  herbarium  material  collected  to 
order.    Sections  to  illustrate  plant  histology  made  to  order. 

B.  Marine  Biological  Laboratory  (Botanical  Supply  Department),  George 
M.  Gray,  Woods  Hole,  Mass.  Preserved  material  of  thallophytes  and 
bryophytes,  mounted  sheets  of  marine  algae. 

C.  H.  M.  Phillips,  19  Warriner  Avenue,  Sprmgfield,  Mass.  Plant  mate- 
rial, especially  fungi. 

D.  St.  Louis  Biological  Laboratory,  St.  Louis,  Mo.  Slides  and  preserved 
material.    See  also  Sec.  219,  B. 

E.  Williams,  Brown  &  Earle,  918  Chestnut  Street,  Philadelphia,  Pa. 
Slides.    See  also  Sec.  218,  K. 

F.  Queen  &  Company,  1010  Chestnut  Street,  Philadelphia,  Pa.  Slides. 
See  also  Sec.  218,  L. 

218.  Apparatus  and  supplies.  Microscopes,  physiological  and  other  appa- 
ratus, glassware,  general  botanical  supplies,  etc.,  are  sold  by  the  dealers 
listed  below  from  price  lists  which  may  be  obtained  from  them. 

A.  BauschjKS:-  Lomb,  Rochester,  N.Y.  Microscopes,  apparatus  especially 
for  plant  physiology,  glassware,  chemicals,  and  general  supplies. 

B.  Cambridge  Botanical  Supply  Company,  Waverley,  Mass.  Physio- 
logical apparatus,  instruments,  special  botanical  equipments,  notebooks, 
general  botanical  supplies. 

C.  James  T.  Dougherty,  409  West  59th  Street,  New  York  City.  Reichert 
microscopes,  apparatus,  glassware,  and  chemicals. 

D.  Eimer  &  Amend,  205  Third  Avenue,  New  York  City.  Glassware, 
chemicals,  and  many  instruments,  general  importers. 

E.  L.  E.  Knott  Apparatus  Company,  16  Ilarcourt  Street,  Boston,  Mass. 
Apparatus  and  supplies  for  general  and  special  purposes. 

F.  Kny-Scheerer  Company,  225  Fourth  Avenue,  New  York  City.  Appa- 
ratus, chemicals,  and  supplies,  importers. 

G.  Ernst  Leitz,  30  East  18th  Street,  New  York  City.  Microscopes,  appa- 
ratus, glassware,  chemicals,  and  general  supplies. 

H.  Spencer  Lens  Company,  Buffalo,  N.Y.  Microscopes,  apparatus, 
glassware,  chemicals,  and  supplies. 


226  MATERIAL,  APPARATUS,  AND  SUPPLIES 

J.  Whitall,  Tatum  &  Co.,  New  York  City.    Glassware. 

K.  Williams,  Brown  &  Earle,  918  Chestnut  Street,  Philadelphia,  Pa. 
Beck  microscopes,  apparatus,  glassware,  and  general  supplies. 

L.  Queen  &  Company,  1010  Chestnut  Street,  Philadelphia,  Pa.  Micro- 
scopes, apparatus,  glassware,  and  general  supplies. 

219.  Lantern  slides  and  charts.    Lantern  slides  are  sold  singly  or  in  sets  by  : 

A.  Cambridge  Botanical  Supply  Company,  Waverley,  Mass. 

B.  St.  Louis  Biological  Laboratory,  St.  Louis,  Mo. 

There  are  a  number  of  sets  of  charts  on  the  market.    The  most  com- 
plete are  : 

C.  Kny.  Botanische  Wandtafeln,  a  series  of  105  so  far  published,  price 
355  Marks.    Paul  Parey,  Hedemannstrasse  10,  Berlin,  S.W. 

D.  Frank-Tschirch.  Wandtafeln  fur  den  Unterricht  in  der  Pflanzen- 
physiologie,  a  series  of  60,  price  180  Marks.  Published  also  by  Paul 
Parey  (see  above). 

A  new  set  of  charts  has  recently  been  announced,  which  promises  well, 

E.  Baur-Jahn.  Tabuloe  BotaniccB,  to  appear  in  series  of  five,  25  Marks  a 
series.  Published  by  Gebriider  Borntraeger,  Dessauerstrasse  29,  Ber- 
lin, S.W. 


BIBLIOGRAPHY 


[Six  books  which  iu  the  opinion  of  the  authors  should  be  in  every 
botanical  library  have  been  double  starred.] 


GENERAL  TEXTS 

**1.  Strasburger,  Noll,  Schenck,  Karsten.  K  Trxt-Hool  of  llotamj.  Third 
revised  translation  by  W.  H.  Lang.  The  Macmillan  Company, 
New  York,  1908.  ^5.00.  The  original  Lehrhuch  der  liotnnik  ap- 
pears in  frequent  revised  editions.   G.  Fischer,  Jena.  Marks  8..'>0. 

2.  Kerner-Oliver.    Natural  History  of  Plants.    Henry  Holt  &  Company, 

New  York,  1905,  two  volumes.    111.00. 

3.  Campbell.    A  University  Text-Book  of  Botany.    The  Macmillan  Com- 

pany, New  York,  1902.    $4.00. 

LABORATORY  MANUALS,  METHODS  OF  TEACHING,  ETC. 

**6.  Strasburger-Hillhouse.    Handbook  of  Practical  Botany.    The  Mac- 
millan Company,  New  York,  1900.    $2.00. 

7.  Ganong.     The  Teaching  Botanist.    The  Macmillan  Company,  New 

York,  1910.    $1.10. 

8.  Lloyd  and  Bigelow.    The  Teaching  of  Biology  in  the  Secondary  School. 

Loiigiuaus,  Green  &  Company,  New  York,  1904.    $1.50. 

9.  Detmer-Moor.    Practical  Plant  Physiology.    The  Macmillan  Com- 

pany, 1898.    $3.00. 

10.  Ganong.    Laboratory  Course  in  Plant  Physiology.    Henry  Holt  & 

Company,  New  York,  1908.    $1.75. 

11.  Darwin  and   Acton.     Practical  Physiology  of  Plants.     University 

Press,  Cambridge,  1897.    $1.25. 

12.  Caldwell.     Handbook  of  Plant  Morphology.     Henry  Holt  &  Com- 

pany, New  York,  1904.    $1.00. 

13.  Osterhout.     Experiments  with  Plants.    The  Macmillan  Company, 

New  York,  1905.    $1.25. 

227 


228  BIBLIOGRAPHY 

MORPHOLOGY 

General 

See  1,  2,  and  3. 

16.  GoebeL    Outlines  of  Classification  and  Special  Morphology  of  Plants. 

Clarendon  Press,  Oxford,  1887.    $5.25. 
Algm 

17.  Oltmanns.    Die  Morphologic  und  Biologic  der  Algen.    G.  Fischer, 

Jena,  1904-1905,  two  volumes.    Marks  36.50. 

18.  West.     Treatise  on  the  British  Fresh-Water  Algoc.    University  Press,^ 

Cambridge,  1904.    $3.50. 

19.  Murray.  An  Introduction  to  the  Study  of  Sea- Weeds.    The  Macmil- 

lan  Company,  New  York,  1895.    $1.75. 
Fungi 

20.  De  Bary.     Comparative  Morphology  and  Biology  of  the  Fungi,  My- 

cetozoa,  and  Bacteria.    Clarendon  Press,  Oxford,  1887.    $5.50. 

21.  Massee.    A  Text-Book  of  Fungi.    The  Macmillan  Company,  New 

York,  1906.    $2.00. 

22.  Fischer- Jones.    The  Structure  and  Functions  of  Bacteria.    Clarendon 

Press,  Oxford,  1900.    $2.10. 
Bryophytes  and  Pteridophytes 

23.  CampbelL     The  Structure  and  Development  of  Mosses  and  Ferns. 

The  Macmillan  Company,  New  York,  1905.    $4.50. 
Gymnosperms 

24.  Coulter  and  Chamberlain.    Morphology  of  Spermatophytes :  Parti, 

Gymnosperms.    D.  Appleton  &  Company,  N.Y.,  1901.    $1.75. 

25.  Penhallow.    A  Manual  of  the  North  American  Gymnosperms.    Ginn 

&  Company,  Boston,  1907.    $4.50. 
Angiosperms 

26.  Coulter  and  Chamberlain.    Morphology  of  Angiosperms.    D.  Apple- 

ton  &  Company,  New  York,  1903.    $2.50. 

27.  Stevens.    Plant  Anatomy.    P.  Blakiston's  Son  &  Company,  Phila- 

delphia, 1907.    $2.00. 

PHYSIOLOGY     , 

**31.  Pfeffer-Ewart.  The  Physiology  of  Plants:  Vol.  I,  Introduction, 
Properties  of  Cells,  Nutrition;  Vol.  11,  Growth,  Variation  and 
Heredity;  Vol.  Ill,  Movements,  Production  of  Heat,  Light, 
and  Electricity,  Transformations  of  Energy.  Clarendon  Press, 
Oxford.  Vol.  I,  1900,  $7.00;  Vol.  II,  1903,  $4.00;  Vol.  Ill, 
1906,  $7.00. 


BIBLIOGRAPHY  229 

32.  Peirce.    Text-Book  of  Plant  Ph>/sin/o;/i/.    Ilciiry  lIuH  ^  Company, 

New  York,  lf)0:3.    .f2.00. 

33.  Haberlandt.     Phijs'iologische  Pfanzemuiatonw'.     Engelmaini,   F.cip- 

zig,  1904.    ]\Iarks  21. 

34.  Green.    An    Introduction   to    Vef/etahle  Physiolo;/!/.     l\   Blakistoii's 

Son  &  Company,  Philadelphia,  1007.    $3.00. 
Detmer-Moor,  see  0.    Ganong,  see  1(). 
Osterhout,  see  13. 
Darwin  and  Acton,  see  11. 

35.  Darwin,  Charles.     The  Power  of  Movement  in  Plants.    D.  Appleton 

&  Company,  New  York,  1900.    $2.00. 


TAXONOMY 

General 

36.  Engler.     Syllabus    der   Pfanzenfamilien.     Gebriider    Borutraeger, 
Berlin,  1907.    Marks  4.50. 
**37.  Warming-Mobius.    Handhuch  der  sijstematischtn  Butanik.    (Jebrikler 

Borntraeger,  Berlin,  1902.    Marks  8. 
Slime  Molds 

38.  Macbride.     The  North  American  Slime  Moulds.     The  Macmillan 

Company,  New  York,  1889.    $2.25. 
Algce 

39.  Engler  and  Prantl.    Die  natiirlichen  Pfanzenfamilien  :  I.  Tell,  Ah- 

teilung  1  «,  Schizomycetes,  Schizophyceoe,  Flagellata ;  I.  Teil, 
Abteilung  1  h,  Peridinales,  Bacillariacese ;  I.  Teil,  Abteihing  2, 
Conjugatge,  Chlorophycea^,  Pha^ophycete,  Rhodophycea).  Engel- 
mann,  Leipzig. 

Oltmanns,  see  17. 

West,  see  18. 

Murray,  see  19. 
I^ungi 

40.  Engler  and  Prantl.    Die  natiirlichen  PjlanzenfamUien  :  I.  Teil,  Ab- 

teilung 1,  Myxomycetes,  Phycomycetes,  Asconiycetes ;   I.  T«m1, 
Abteilung  1**,  Basidiomycetes,  Fungi  imperfecti.    Engelmann, 
Leipzig. 
Massee,  see  21. 

41.  Atkinson.    Mushrooms.    Henry  Holt  &  Company,  New  York,  1903. 

$3.00. 
Lichens 

42.  Schneider.    A  Guide  to  the  Study  of  Lichens.    Bradlee  Whiddeu, 

Boston,  1898.    $1.90. 


230  BIBLIOGRAPHY 

Liverworts  and  Mosses 
Gray,  see  46. 

43.  Grout.    Mosses  with  Hand-Lens  and  Microscope.    Published  by  the 

author,  360  Lenox  Road,  New  York  City,  1903-1906.    |3.75. 
Campbell,  see  23. 
Ferns  and  Fern  Allies 
Gray,  see  46. 

44.  Underwood.     Our  Native  Ferns  and  Their  Allies.    Henry  Holt  & 

Company,  New  York,  1899.    $1.00. 

45.  Clute.     The    Fern    Allies    of   North    America    North    of  Mexico. 

Frederick  A.  Stokes  &  Company,  New  York,  1905.    |2.00. 
Campbell,  see  23. 
Seed  Plants 

46.  Gray.    Manual  of  Botany  of  the  Northern  United  States.    American 

Book  Company,  New  York. 

47.  Gray,  Watson,  Robinson.     Synoptical  Flora  of  North  America.    A 

monographic  treatment  of  I,  Gamopetalce  (Smithsonian  Institu- 
tion, 1886,  12.50);  II,  Polypetaloi,  Voh  I,  Fas.  1  and  2,  Ranun- 
culaceae  to  Polygalaceae  (American  Book  Company,  $5.20). 

48.  Britton.    Flora  of  the  Northern  States  and  Canada.    Henry  Holt  & 

Company,  New  York.    <|2.25. 

49.  Gray.    Field,  Forest,  and  Garden  Botany.    American  Book  Com' 

pany.  New  York,  1895.    $1.44. 

50.  Sargent.     Manual  of  the   Trees  of  North  America  (exclusive  of 

Mexico).    Houghton,  Mifflin  &  Company,  Boston,  1905.    $6.00. 

51.  Chapman.    Flora  of  the  Southern  United  States.    American  Book 

Company,  1897.    $3.60. 

52.  Coulter.     Manual  of  Rocky   Mountain  Botany.    American    Book 

Company,   New  York,  1885.     $1.62. 

ECOLOGY  AND  PLANT  GEOGRAPHY 

56.  Schimper-Fisher.     Plant    Geography.     Clarendon    Press,    Oxford, 

1903.    $14.00. 

57.  Warm ing-Groom-Balf our.     (Ecology    (f  IHants.     Clarendon  Press, 

Oxford,  1909.    $2.90. 

58.  Pound  and  Clements.    Phytogeography  of  Nebraska.    University  of 

Nebraska,  Lincoln,  Nebraska,  1900.    $2.00. 

59.  Clements.     Research  Methods  in  Ecology.    University  Publishing 

Company,  Lincoln,  Nebraska,  1905.    $3.00. 


BIBLIOGPvAPIIV  231 

60.  Wiesner.    Biologie  der  PJlanzcn.    A.  IIoldtuM-,  Wiini,  1  Hol .    .M;irks 

10.20. 

61.  Ludwig.     Lehrhuch  Her  Pjlanzcuhiolofjii.     Kiikc,  Stuttgart,  1805. 

Marks  16. 

62.  Knuth-Davis.    Handbook  of  Flower  Pollination.    Claroiidon  Pre.s.s, 

Oxford,  1906-1909,  three  volumes.    .f27.25. 

63.  Beal.    Seed  Dispersal.    Ginn  &  Company,  Boston,  1898.    lio  cents. 

64.  Darwin,  Charles.    Insectivorous  Plants.    D.  Appleton  &  Comi)any, 

New  York,  1900.    12.00. 


EVOLUTION 

**66.  Darwin,  Charles.    The  Origin  of  Species.    D.  Appleton  &  Comj»any, 
New  York,  1906.    $2.00. 

67.  De  Vries-Farmer-Darbishire.     The  Mutation   Theon/.     Open  Couit 

Publishing  Company,  Chicago,  1909-1910,  two  volumes.   .^8.0(1. 

68.  Bailey.     The  Survival  of  the  Unlike.    The  Macmillan  Comjiany. 

New  York,  1899.    $2.00. 

69.  Darwin,  Charles.     Variation  of  Animals  and  Plants  under  Domesti- 

cation.   1).  Appleton  &  Company,  New  York,  1900,  two  volumes. 
$5.00. 

70.  Campbell.    l^hDit   Lif'  and    I'^rolution.     Henry  Ilolt  ^c  C()mi»any, 

New  York,  1911.    $1.7.-). 


ECONOMIC   BOTANY 

71.  United  States  Department  of  Agriculture.    Procure  lists  of  publica- 

tions from  Superintendent  of  Documents,  (iovernment  Printing 
Office,  Washington,  D.C.  Important  papers  appear  fretpiently, 
which  may  be  obtained  at  small  cost. 

72.  Agricultural  Experiment  Stations.    These  issue   many  important 

circulars,  bulletins,  and  rei)orts.  For  addresses  of  the  statf  pro- 
cure the  Organization  Lists  of  Agricultural  Experiment  Stations 
from  the  Superintendent  of  Docunu'uts  (address  above).  Price 
of  list,  10  cents. 
**73.  Bailey.  Plant  Breeding.  The  Macmillan  Company,  Xew  York. 
1906.  $1.25. 
74.  Tschirch.,  Angeivandte  Pjlanzenanatomie,  Erster  Band.  Urban  \ 
Schwarzenberg,  Wien,  1889.    $4.50. 


232  BIBLIOGRAPHY 

75.  Roth.    First  Book  of  Forestry.     Ginn  &  Company,  Boston,  1902. 

75  cents. 

76.  Pinchot.    A  Primer  of  Forestry :    Part  I,   The  Forest ;    Part  II, 

Practical  Forestry.  United  States  Department  of  Agriculture, 
Bureau  of  Forestry,  Bulletin  24  :  Part  I,  1899,  35  cents ;  Part 
II,  1905,  30  cents. 

77.  Tubeuf-Smith.    Diseases  of  Plants.    Longmans,  Green  &  Company, 

New  York,  1897.    $5.50. 

78.  Freeman.    Minnesota  Plant  Diseases.    Published  by  the  University 

of  Minnesota,  Minneapolis,  1905. 

79.  Conn.    Agricultural  Bacteriology.    P.  Blakiston's  Son  &  Company, 

Philadelphia,  1901.    $2.50. 

80.  Conn.    Bacteria,  Yeasts,  and  Molds  in  the  Home.    Ginn  &  Company, 

Boston,  1903.    $1.00. 

81.  Lafar-Salter.     Technical   Mycology.    J.    B.    Lippincott,    Philadel- 

phia: Vol.  I,  1906,  $4.00;  Vol.  II,  1903,  $2.50. 

82.  Whipple.    The  Microscopy  of  Drinking  Water.    John  Wiley  &  Sons, 

New  York,  1905.    $3.50. 

83.  Willis.    Practical  Flora.    American  Book  Company,  New  York, 

1894.    $1.50. 

MISCELLANEOUS 

86.  Carnegie  Institution.    Procure  lists  of  publications  from  the  Car- 

negie Institution  of  Washington,  Washington,  D.C.  Important 
papers  appear  frequently,  which  may  be  obtained  at  moder- 
ate cost. 

United  States  Department  of  Agriculture,  see  71. 

Agricultural  Experiment  Stations,  see  72. 

87.  Winslow.    Elements  of  Applied  Microscopy.    John  Wiley  &  Sons, 

New  York,  1905.    $1.50. 

88.  Jackson.    Glossary  of  Botanical  Terms.    J.  B.  Lippincott  Company, 

Philadelphia,  1906.    $2.00. 

ADDENDA 

Goebel-Balfour.    Organography  of  Plants.    Clarendon  Press,  Oxford, 
1900-1905,  two  volumes.   $11.75. 


APPENDIX 


1.  Laboratory  notes.  Much  of  the  value  of  lal)oratory  work  must 
always  depend  upon  the  way  in  which  the  notebooks  are  inHpecte<l. 
Those  with  detached  leaves,  which  may  be  assembled  in  some  kind  of 
binder,  are  to  be  preferred;  and  the  instructor  may  certify  his  accept- 
ance of  the  notes,  page  by  page,  either  during  the  laboratory  period 
or  immediately  afterward.  In  general,  unsatisfactory  notes  should  be 
rewritten  from  new  studies  of  the  material  in  question  or  (better)  of 
equivalent  forms. 

Valuable  data  of  any  sort  secured  during  the  year's  work  should  be 
preserved  for  subsequent  use.  In  this  way,  for  example,  the  optimum 
conditions  for  many  of  the  phenomena  of  plant  life  may  be  ascertained 
by  assembling  the  results  of  the  best  student  observers.  Duplicates  of 
photographs  and  drawings  may  be  kept  in  the  botanical  museum. 

2.  Students'  preparations.  In  all  cases  in  whicli  the  student  finds  it 
advisable  to  make  for  himself  a  set  of  preparations,  e.g.  of  slides  to 
illustrate  any  histological  topic,  such  preparations  should  be  treated  as 
a  part  of  his  laboratory  record.  A  duplicate  series  for  the  laboratory 
can  usually  be  made  with  little  extra  effort.  In  the  same  way  preserved 
material  illustrating  the  life  history  of  the  plant,  its  variations  as  a 
whole,  or  the  modifications  of  its  parts  under  varying  environmental 
conditions,  may  be  added  to  the  museum  or  other  general  collections. 

3.  Sources  of  material.  Aside  from  the  obvious  sources  of  material  for 
morphological  and  still  more  for  histological  study  (such  as  tlir  wild 
seed  plants  of  the  region,  gardens,  and  greenhouses)  there  are  others 
not  less  valuable.  A  very  large  number  of  admirable  subjects  for  histo- 
logical work  can  be  had  from  the  wholesale  druggists,  particularly  those 
who  make  a  specialty  of  "  botanical  "  remedies.  Almost  any  i»art  of  the 
plant  body  may  be  used  in  medicine,  and  many  oflicinal  substances, 
such  as  calisaya  bark,  the  young  wood  of  S(tianum  dulcaiiiarii,  the  root- 
stock  of  Acorus,  the  fruits  of  many  UmheUifera\  and  a  great  number  oi 
other  substances,  to  be  had  of  dealers  in  drugs,  form  excellent  matcriaJ 

233 


234  APPENDIX 

for  study.  Seeds,  bull)S,  and  rootstocks  in  great  variety  can  be  had  of 
the  seedsmen,  and  much  useful  material  may  he  found  among  the  fruits 
and  vegetables  sold  by  marketmen  or  provision  dealers  all  the  year 
round.  Dealers  in  fine  lumber  and  cabinet  woods  can  supply  many  kinds 
which  are  of  histological  interest. 

4.  Collection  of  material  at  the  proper  season.  In  many  cases  the  useful- 
ness of  material  depends  largely  on  its  being  collected  at  just  the  right 
stage  of  maturity  or  at  some  particular  season.  Experience  will  show 
the  instructor  at  what  time  he  can  in  his  special  locality  best  lay  in  the 
stock  for  his  year's  work.  A  few  examples  only  need  here  be  mentioned. 
Green  corn  (best  of  the  large  "  dent "  variety),  just  passing  out  of  the 
milky  condition,  should  be  collected  and  boiled  in  water  for  about 
twenty  minutes.  It  is  then  to  be  sliced  from  the  cob,  cutting  deeply 
enough  to  preserve  the  embryos  uninjured.  The  grains  thus  prepared 
may  be  preserved  in  alcohol  indefinitely  for  study  of  the  entire  embryo. 

Bean  fruits  of  all  ages,  from  the  newly  fertilized  pistil  to  the  fully 
developed  but  not  dry  pod,  should  be  collected  in  season  and  put  in 
preservative  fluid,  such  as  formalin,  to  illustrate  the  development  of  a 
fruit.  If  convenient,  series  of  stages  in  the  development  of  other  fruits, 
e.g.  apple,  strawberry,  orange,  should  be  secured. 

Indian  corn  plants  should  be  dug  up  at  various  stages  of  growth  and 
the  lower  part  of  the  stem,  with  the  attached  roots,  dried  and  preserved, 
after  being  thoroughly  washed.  These  will  illustrate  secondary  roots 
and  successive  steps  in  the  formation  of  aerial  roots.  Pieces  of  corn 
stem  of  various  ages  show  the  development  of  bundles  and  of  the  very 
hard  sclerenchyma  of  the  rind. 

Bits  of  Arktolochia  or  other  stem  used  to  illustrate  open  bundles 
should  be  collected  in  early  summer,  as  soon  as  these  are  found  to  be 
well  developed.  A  series  of  such  stems  cut  at  short  intervals  through- 
out the  growing  season  is  valuable. 

Leaves  of  deciduous  trees  or  shrubs  should  be  collected  as  soon  as 
fully  grown  and  again  when  about  to  fall,  and  preserved  in  alcohol 
for  the  study  of  translocation  of  starch  before  falling. 

Series  of  herbarium  sheets  and  of  specimens  in  preservative  fluid 
should  be  secured  to  show  the  seasonal  cycle  of  such  plants  as  Erythro- 
nium,  Sanguinaria,  and  many  similar  forms. 

5.  Field  work.  Many  botanical  topics  can  best  be  taught  and  some 
can  only  be  taught  in  the  field.     It  may  be  found  desirable  to  interweave 


APPENDIX  235 

instruction  in  ecological  toi)ics  dmiiit;  fi<'l<l  tiips  jiiirnaiiiy  uiMlcrtakf^n 
for  other  purposes.  So  much  depends  (m  tiic  naliin' of  IIm-  n-gioii  in 
which  the  work  is  done,  the  maturity  of  the  class,  the  amount  of  time 
available  for  out-of-door  study,  and  other  circumstances,  that  only  a  few 
general  principles  for  field  w^ork  are  here  suggesU'd. 

(rt)  Every  expedition  should  have  one  definite  jiurposc  If  many 
incidental  subjects  come  up,  they  must  not  intrrft-ie  with  the  i>rimary 
object  of  the  trip. 

(/>)  All  observations  must  be  exact.  If  it  is  desired  to  ascertain  the 
composition  of  a  plant  association,  the  number  of  si)ecies  and  individuals 
occurring  in  measured  units  of  area  should  be  ascertained  by  actual 
count. 

Temperatures  of  air,  soil,  or  water  should  be  noted  with  a  good 
thermometer. 

Illumination  (in  shaded  areas)  should  be  measured  at  several  periods, 
e.g.  two  hours  after  sunrise,  noon,  and  two  hours  before  sunset. 

In  some  cases  it  maybe  practicable  to  determine  the  relative  moisture 
of  the  soil  of  several  stations  for  at  least  the  driest  period  of  the  year. 
Such  results  should  be  kept  on  record  and  may  be  taken  into  account 
by  all  classes  which  thereafter  discuss  the  vegetation  of  those  areas. 

(c)  The  distribution  of  vegetation  forms  must  be  studied  with  refer- 
ence to  extreme  conditions.  Xerophytic  structure  does  not  always  serve 
as  a  protection  against  a  low  annual  rainfall  but  rather  against  severe 
periods  of  drought. 

(d)  Reasoning  on  ecological  topics  should  be  conducted  with  great 
caution.  It  is  not  safe  to  assume  that  attractiveness  in  any  part  of  the 
plant  body,  as  in  the  sweet  cambium  layer  of  the  white  pine  or  tlie 
inner  bark  of  the  slippery  elm,  is  always  of  use  to  the  plant.  It  may  be 
highly  disadvantageous.  On  the  other  hand,  such  "defenses"  as  the 
thorns  on  the  trunk  of  the  honey  locust  tree  are  of  little  or  no  conceiv- 
able use  (on  the  branches  they  may  be  advantageous). 

6.  The  study  of  Spirogyra.  It  is  important  to  proceed  slowly  wh.n 
students  begin  to  use  the  compound  microscope,  and  to  make  sure  that 
correct  habits  of  work  are  formed.  The  power  to  visualize  or  interpret 
objects  studied  with  the  compound  microscope  should  be  carefully 
trained.  Simple  models  may  be  constructed.  Thus  the  structure  of  the 
cell  of  Spirogyra  may  be  demonstrated  very  effectively  with  a  glass  jar 
to  represent  the  cell  wall,  a  paper  bag  for  the  living  i>lasma  membrane, 


236  APPENDIX 

strips  of  paper  properly  wound  inside  to  represent  the  chromatophore, 
and  some  object  suspended  in  the  center  to  illustrate  the  position  of  the 
nucleus.  A  simple  model  of  this  character  made  with  the  cooperation  of 
the  class  will  greatly  assist  the  students  to  a  clear  understanding  of  the 
study  outlined  in  Sec.  56. 

Whenever  possible,  a  study  of  the  Amoeba  or  Euglena  in  comparison 
with  the  cell  of  Spirogyra  will  be  found  very  helpful  in  making  clear 
the  characteristics  of  a  protoplast. 

Stained  preparations  of  Spirogyra  filaments  (Sec.  211)  may  help  to 
an  understanding  of  the  cell  structure,  but  in  general  it  is  better  that 
the  student  handle  living  material  and  with  the  aid  of  a  few  simple  re- 
agents (such  as  iodine  and  the  salt  solution)  discover  the  facts  for 
himself. 

7.  Cultures  of  Amoeba.  Cultures  of  Amoeha  may  be  made  in  an  aqua- 
rium jar  overstocked  with  filamentous  algae.  Introduce  sediment  from 
a  pool  of  Oscillatoria  with  a  mass  of  the  algae ;  growths  of  Scenedesmus 
are  also  likely  to  have  Amoeb(B.  Place  the  jar  near  a  window  but  just 
out  of  the  direct  rays  of  the  sun.  The  filamentous  algae  will  decay  and 
after  a  few  weeks  a  coating  will  be  formed  on  the  sides  of  the  jar. 
From  this  coating  or  from  the  sediment  on  the  bottom  of  the  jar 
Amoebce  can  usually  be  obtained  in  quantity.  They  are  generally  most 
abundant  on  the  sides  nearest  the  light.  In  preparing  material  for  the 
class  gather  a  quantity  of  the  slime  and  sediment  with  a  pipette  and 
place  in  a  small  bottle.  After  a  few  hours  the  water  at  the  top  will 
frequently  contain  so  many  Amcebce  that  the  students  may  readily  find 
them  in  mounted  drops. 

8.  Nuclear  and  cell  division.  Nuclear  and  cell  division  may  also  be 
studied  from  preparations  of  the  pollen  mother  cells  of  the  lily  (Sec.  141) 
and  in  sections  of  various  growing  tissues  such  as  stem  tips,  developing 
ovules,  embryo  sacs  of  lily,  etc. 

9.  Cultures  of  Euglena.  A  culture  of  Euglena  in  a  shallow  dish  with 
leaves  and  sediment  at  the  bottom  may  be  allowed  to  slowly  dry  up  by 
evaporation.  The  Euglence  will  pass  into  the  encysted  condition.  This 
dish  of  dried  material  may  then  be  placed  aside  and  will  keep  indefi- 
nitely. If  water  be  added,  the  encysted  Euglence  will  come  forth  again 
in  the  motile  condition. 

10.  Sphaerella  and  Volvox.  If  stones  are  placed  in  a  dish  swarming 
with  Sphcerella,  the  motile  cells  will  settle  upon  them  and  pass  into  a 


APPENDIX  237 

resting  stage  in  which  the  cells  develop  heavy  walls  and  the  conU'nts 
become  reddish.  Such  stones  may  be  dried,  and  when  placed  again  in 
rain  water  will  develop  anew  generation  of  green  motile  cells.  Cultures 
may  thus  be  carried  along  from  season  to  season.  The  oosporps  of 
Volvox  will  fall  to  the  bottom  of  an  aquarium  among  the  sediment  and 
after  a  time  produce  a  new  generation  of  Volvox  colonies. 

11.  Hydrodictyon.  Hydrodictyon  may  be  readily  grown  in  aquaria, 
where  it  will  form  successive  generations  of  nets.  INIaterial  cultivated 
in  diluted  Knop's  solution,  one  half  to  one  per  cent  (Sec.  200,  A),  is 
likely  to  form  zoospores  after  a  few  hours  if  transferred  to  pond  or  tap 
water.  Nets  placed  in  a  five  per  cent  solution  of  cane  sugar  (Sec.  200,  C) 
are  likely  to  produce  gametes  in  a  few  days. 

12.  Coleochaete.  Coleochcete  frequently  appears  in  aquaria,  forming 
green  disks  on  the  sides  of  the  glass.  These  may  readily  be  detached 
with  a  scalpel  and  gathered  with  a  pipette,  and  show  the  vegetative 
structure  of  the  plant  excellently.  We  have  never  known  the  alga  to 
produce  sexual  fruit  in  aquaria. 

13.  Diatoms.  The  shells  of  diatoms  in  polishing  powders  and  earths, 
or  masses  of  fresh  material,  may  be  cleaned  as  follows.  Heat  in  a  small 
porcelain  evaporator  with  c.p.  sulphuric  acid  and  slowly  drop  in  a  few 
crystals  of  sodium  nitrate.  After  cooling  rinse  the  sediment  thoroughly 
in  water,  decanting  frequently.  It  may  then  be  dried  on  a  slide  and 
mounted  permanently  in  balsam. 

14.  Bacteria.  It  is  much  more  important  that  the  bacteria  l)e  studied 
for  the  appearance  of  the  growths  en  masse  than  that  detailed  micro- 
scopical examinations  be  made  of  these  minute  organisms.  Tl>e  micro- 
scopical examination  of  the  "  fur  "  from  the  teeth  gives  one  of  the  most 
striking  assemblages  of  forms.  The  cultures  are  best  made  by  groups  of 
students  working  with  a  set  of  Petri  dishes  in  common.  Excellent  cul- 
tures of  bacteria  may  be  obtained  in  Petri  dishes  on  potato  agar  as  a 
substratum  (Sec.  203),  and  these  are  preferable  to  cultures  on  slices  of 
potato,  but  the  preparation  of  agar  requires  more  time  and  considerable 
laboratory  equipment. 

15.  The  bread  mold.  Individual  cultures  of  bread  mold  may  be 
readily  made  by  the  students  and  are  more  convenient  for  study  than  a 
large  culture  in  common.  Place  small  pieces  of  bread  in  watch  glasses 
and  set  the  latter  over  wet  blotting  paper  in  saucers,  covering  each  with 
a  tumbler.    To  make  sure  of  good  growths  inoculate  the  pieces  of  bread 


238  APPENDIX 

with  spores  from  an  old  culture.  These  small  cultures  can  be  readily 
handled  and  studied  with  the  hand  lens,  especially  portions  of  the 
mycelium  which  may  grow  out  over  the  surface  of  the  watch  glass. 
The  bread  mold  is  almost  invariably  followed  by  extensive  growths  of 
the  green  mildew,  Penicillium. 

16.  Lichens.  When  time  is  limited  it  is  more  important  that  the 
lichen  be  studied  than  such  Ascomycetes  as  Microsphcera  or  Peziza,  since 
most  lichens  show  excellently  the  fruiting  characters  of  the  sac  fungi. 
The  remarkable  associations  of  fungi  and  algse  to  form  these  composite 
organisms  gives  the  lichens  peculiar  interest.  A  variety  of  lichens 
should  be  collected,  dried,  and  fastened  to  cards  for  comparative  studies 
of  growth  habits  and  form. 

17.  Gill  fungi.  The  study  of  gill  fungi  must  frequently  be  made  at 
times  inconvenient  or  impossible  for  field  trips.  The  laboratory  work 
may  then  be  upon  material  preserved  in  strong  alcohol  or  on  edible 
forms  sold  in  the  markets  (the  commonest  is  Agaricus  campestris^. 
Horse  manure  placed  under  a  bell  jar  will  give  excellent  material  of 
some  small  and  delicate  species  of  Coprinus,  the  development  of  which 
will  prove  interesting. 

18.  Diagrams  and  formulae  illustrating  alternation  of  generations.  The 
difficult  subject  of  alternation  of  generations  may  generally  be  made 
clearer  if  the  chief  phases  in  the  life  histories  of  the  types  studied  are 
represented  by  a  series  of  diagrams.  It  is  helpful  if  the  diagrams  are 
drawn  with  colored  pencils ;  thus  the  gametophyte  phases  may  be  rep- 
resented in  yellow  and  the  sporophyte  phases  in  green.  Life-history 
formulae  may  be  constructed  after  the  manner  suggested  in  the  Princi- 
ples, pp.  222,  278,  319,  336,  and  375. 

19.  Mosses.  Field  studies  of  the  mosses  may  not  be  possible  at  the 
time  the  type  is  studied  in  the  laboratory.  However,  dried  material  is 
generally  very  satisfactory  for  habit  studies  on  a  variety  of  forms,  and 
the  greenhouses  and  cultures  (Sec.  207)  may  be  depended  upon  to  fur- 
nish living  material.  Moss  spores  will  generally  germinate  in  sweetened 
water. 

20.  Ferns.  A  variety  of  ferns  may  be  easily  cultivated  in  the  labora- 
tory, which  with  herbarium  material  will  give  a  very  good  idea  of  dif- 
ferent forms  of  stems  and  leaves.  A  simple  study  of  stem  structure  may 
be  made  by  cutting  across  stems  and  whittling  them  lengthwise.  Such 
an  examination  will  make  clear  at  least  the  position  and  importance 


APrp:NJ)IX  230 

of    the  rigid  tissue  and  fibro-vascular  bundles.     Fern  spores  may  be 
germinated  in  sweetened  water. 

21.  The  pine.  The  pine  is  one  of  the  best  types  of  seed  plants, 
easily  available,  to  make  clear  the  relationships  between  pteridophytes 
and  spermatophytes.  The  general  homologies  between  the  staniinate 
cone  and  the  cones  of  the  club  mosses  and  horsetails  are  easily  un<ler- 
stood,  as  well  as  the  homologies  between  the  pollen  grain  with  its 
inclosed  male  gametophyte  and  the  microspores  of  pteridophytes  with 
their  male  prothallia.  The  female  gametophyte  of  the  pine,  also,  is 
readily  compared  with  the  reduced  female  prothallia  of  heterosporous 
pteridophytes.  For  these  reasons  the  life  history  of  the  pine  is  more 
easily  understood  with  reference  to  the  life  histories  of  pteridoi>hytes 
than  is  the  life  history  of  an  angiosperm  (such  as  the  lily)  where  the 
gametophytes  are  much  more  reduced  in  structure. 

The  pine  is  also  excellent  for  the  study  of  the  tissues  of  a  ti-ee  with 
annual  growth  from  a  cambium  ring.  The  structure  of  pine  woo<l  is  one 
of  the  best  exercises  in  the  interpretation  of  cell  structm-e,  and  the  study 
outlined  in  Sec.  138,  C,  5,  is  often  given  as  a  laboratory  problem. 

In  a  course  outlining  the  evolution  of  life  histories  in  plants  the  pine 
is  as  important  a  type  as  Sclnf/inella,  the  fern,  or  the  moss,  besides  having 
in  itself  a  remarkably  interesting  morphology  in  relation  to  peculiar  life 
habits. 

22.  The  lily.  There  are  perhaps  no  types  more  convenient  than 
those  of  the  lily  family  for  the  study  of  the  gametophytes  of  the  angio- 
sperms.  It  is,  however,  not  easy  to  present  the  life  history  of  angio- 
sperms  in  full  from  the  study  of  a  single  i^i^e  in  a  general  course.  It  is 
probably  better  to  use  various  forms  which  may  be  especially  favorable 
for  particular  phases  ;  as,  for  example,  the  lily  for  the  development  of 
the  pollen,  but  the  elder  for  the  male  gametoj^hyte  ;  the  lily  for  the 
development  of  the  embryo  sac  together  with  fertilization,  ilouble 
fertilization,  and  the  origin  of  the  endosperm,  but  the  shepherd's  i)urso 
for  the  development  of  the  ovule  and  embryo. 

23.  The  shepherd's  purse.  This  j^lant  would  be  almost  jx'rfect  for  a 
complete  study  of  an  angiosperm  life  history  were  it  not  ft»r  the  small 
size  of  the  flowers,  anthers,  and  pistil,  and  in  conset|uence  the  minute- 
ness of  the  gametophytes.  However,  the  shepherd's  purse  is  one  of  the 
best  types  for  the  study  of  floral  develoi)ment  (not withstanding  (•••rtaiu 
irregularities)  and  the  development  of  the  ovule  and  embryo. 


GLOSSARY 


Actinomorphic  (ray  shaped).    Having  star-like  or  radiating  symmetry. 

^cidium.  A  fructification  peculiar  to  certain  rusts  producing  .-rcidio- 
spores,  —  a  cluster  cup. 

Alternation  of  generations.  The  alternation  in  a  life  history  of  a  srxual 
generation  or  ga7tiefoph>/(e  with  an  asexual  generation  or  apornphytr. 

Anemophilous  (wind  loving).  A  term  applied  to  plants  which  an*  pol- 
linated by  the  wind, 

Angiosperms  (vessel  seed).  Plants  which  have  the  seeds  inclosed  in  an 
ovary  or  seed  case. 

Anther  (flowering).    The  part  of  a  stamen  which  bears  pollen. 

Antheridiophore  (antheridia  bearer).  In  the  liverworts  a  specialized 
receptacle  bearing  antheridia. 

Antheridium.  The  male  sexual  organ  producing  sperms  or  antherozoids 
in  the  groups  below  the  seed  plants ;  also  called  an  antherid. 

Antherozoid.    See  Sperm. 

Antipodal  (against  the  foot).  The  term  applied  to  three  cells  at  the  base 
of  the  embryo  sac. 

Apical.    Pertaining  to  the  apex  or  tip. 

Apical  cell.    A  terminal  cell  which  constitutes  a  growing  point. 

Apogamy.  The  development  of  an  egg  without  fertilization,  or  the  devel- 
opment of  a  sporophyte  generation  as  a  bud-like  outgrowth  from  the 
gametophyte. 

Apospory.  The  suppression  of  spore  formation  and  the  devehipmiMit  of 
a  gametophyte  generation  directly  from  the  sporophyte. 

Apothecium.  In  sac  fungi,  Ascomycetes  (including  lichens),  the  open 
cup-  or  saucer-shaped  fructification  in  which  the  sacs  or  asci  lie  ex- 
posed in  a  membrane  or  hymenium. 

Archegoniophore  (archegonia  bearer).  In  the  liverworts  a  speciali/.eil 
receptacle  bearing  archegonia. 

Archegonium  (beginning  of  offspring).  The  many-celled  feiiiah'  sexual 
organ  producing  an  egg,  characteristic  of  the  bryophytes,  pterido- 
phytes,  and  some  gymnosperms. 

Archesporium  (beginning  of  a  spore).  The  cell  or  cells  constituting  the 
tissue  from  which  the  spores  of  bryophytes  and  pteridophytes  are 
ultimately  derived  and  also  their  homologues,  the  i)ollen  grains. 

1  Most  of  the  nouns  in  this  glossary  form  their  phirals  I»y  tlie  a<i.litioii  of  .vor  cs, 
like  ordinary  English  nouns.  Those  ending  in  ks.  unless  otiierwise  stateil.  form 
the  plural  in  i,  as  «uc'/ea.s,  plu.  nuclei.  Those  ending  in  ium  form  tlie  plural  in 
ia,  as  antheridium,  plu.  antheridia. 

241 


242  GLOSSARY 

Ascocarp  (sac  fruit).    The  fructification  in  which  asci  are  formed. 
Ascogonium  (sac  offspring).    The  female  sexual  organ  of  the  sac  fungi, 

or  Asco7n>/cet€s. 
Ascospores  (sac  spores).    The  spores  developed  in  the  ascus. 
Ascus  (a  sac).    One  of  the  spore-producing  cells  of  an  ascocarp;  each 

ascus  generally  develops  eight  spores. 
Asexual  spore.    One  having  no  immediate  relation  to  sexual  cell  unions. 
Association.    One  of  the  ecological  unit  groups  (smaller  than  a  plant 

formation)  of  which  the  formation  is  sometimes  made  up. 
Axial.    Concerning  or  belonging  to  the  axis. 
Axil  (the  armpit).    The  upper  angle  formed  by  the  junction  of  the  leaf 

and  stem. 
Axis   (an  axle).    An  imaginary   central  line  about  which   organs  are 

developed  or  ranged. 

Basidium  (a  little  pedestal).    A  spore-bearing  cell  in  the  basidia  fungi. 
Bast,  hard.    The  fibrous  portion  of  the  phloem. 
Bast,  soft.    The  portion  of  the  phloem  composed  of  sieve  tubes. 
Bilateral  symmetry.    The  arrangement  of  parts  in  corresponding  right 

and  left  halves,  —  zygomorphism. 
Bisexual.    Term  used  of  flowers  having  both  stamens  and  pistils. 
Bract.    A  modified  leaf  of  an  inflorescence. 
Bryophytes  (moss  plants).    The  great  group  composed  of  the  liverworts 

and  mosses. 
Bulb.    A  short  subterranean  stem  or  bud  with  fleshy  scales. 

Calyptra  (a  veil).    The  cap  covering  the  developing  spore  case  of  a  moss 

(and  also  a  liverwort),  formed  by  the  enlargement  of  the  archego- 

nium  after  fertilization. 
Calyx  (a  cup).    A  collective  term  for  the  sepals  or  outer  members  of  the 

perianth. 
Cambium  (to  change).    The  meristematic  layer  which  in  dicotyledons 

lies  between  the  xylem   and  phloem  parts  of  each   fibro-vascular 

bundle  and  forms  a  very  thin  cylinder  joining  wood  and  bark. 
Canal  cells.    A  row  of  cells  in  the  neck  of  an  archegonium  above  the  egg. 
Capsule  (a  box).    A  dry,  dehiscent  seed  vessel. 
Carpel  (fruit).    The  simplest  form  of    seed-bearing  organ  ;    a    simple 

pistil  or  one  of  the  parts  of  a  compound  pistil  ;  morphologically  a 

mefjasporophyll. 
Carpogonium   (fruit  offspring).    The  female    sexual   organ  of    the  red 


Carpospore  (fruit  spore).    A   spore  developed  in  the  cystocarp  of  a  red 

alga. 
Cell  (a  small  chamber).    A  unit  of  protoplasm  ;  a  protoplast  {yf\i\\  or 

without  a  cell  wall). 
Cell  wall.    The  carbohydrate  membrane,  generally  cellulose,  by  which 

plant  protoplasts  are  usually  inclosed. 


GLOSSARY  243 

Cellulose.    The  carbohydrate  material  of  whicli  roll  walls  arc  formed. 

Central  cylinder.  The  stele  or  portion  of  a  root  or  stein  whicii  is  inclosed 
by  the  primary  cortex. 

Chlamydospore  (cloaked  spore).    A  thick-walled  resting'  cell  or  spore. 

Chlorophyll  (leaf  green).  Tlie  ordinary  green  coloring  matter  of  plants 
held  in  the  chloroplasts,  or  chromatophores. 

Chlorophyll  bodies.  Masses  of  protojdasm  (in  seed  plants  nsnally  minute 
disk-shaped  bodies)  colored  green  by  clilorophyll,  —  chloroplasts. 

Chloroplasts  (green  molded).  Chlorophyll  bodies;  plastids  containing 
chlorophyll. 

Choripetalous  (separate  petal).    Having  the  petals  separate. 

Chorisepalous  (separate  sepal).    Having  the  sepals  separate. 

Chromatin  (color).  The  deeply  staining  substance  contained  in  the 
nucleus  which  forms  the  chromosomes. 

Chromatophore  (color  bearer).  Any  large  green,  brown,  or  red  proto- 
plasmic body,  especially  characteristic  of  the  cells  of  alg;e. 

Chromoplast  (color  molded).  Plastids  of  other  colors  than  green  (as 
red,  brow^n,  yellow,  etc.),  a  term  used  in  contrast  to  chloroi'last. 

Chromosomes  (color  bodies).  Readily  stained  bodies  w  ithin  the  nucleus, 
composed  of  chromatin  and  appearing  most  cons})icuously  during 
nuclear  division. 

Cilium  (an  eyelash).    A  vibrating  fibril  attached  to  a  zoiispore  or  sperm. 

Cladophyll  (branch  leaf).  A  brancli  with  the  form  and  functions  of  a 
leaf,  called  also  a  cladode  and  phylloclade. 

Class.    A  taxonomic  group  composed  of  orders. 

Cleistogamous  (closed  marriage).  A  term  apjtlied  to  fertilization  occur- 
ring in  unopened  flowers. 

Closed  bundle.  A  fibro-vascular  bundle  which  contains  no  cambium 
and  is  consequently  incapable  of  further  growth. 

Ccenocyte  (a  vessel  in  common).  A  multinucleate  eell.  gent'rally  of 
large  size. 

Ccenogamete  (a  gamete  in  common).  A  multinucleate  gamete,  gen- 
erally of  large  size. 

Collenchyma.  Parenchyma  cells  with  walls  thickened,  usually  at  the 
angles. 

Columella,  plu.  columella;  (a  small  column).  The  persistent  axis  of  cer- 
tain spore  cases  and  spore  fruits. 

Companion  cell.    An  elongated  cell  associated  with  a  sieve  tube. 

Conceptacle.  A  pit-like  cavity  in  the  rockweeds  containing  the  .sexual 
organs. 

Cone.  The  scaly  fruit  of  such  conifers  as  the  pines,  si»ruces,  etc.,  also 
of  the  lyco])ods  and  horsetails,  —  a  strobilus. 

Conidiophore  (conidia  bearer).  A  generally  upright  stalk  upon  Nshich 
coiiidia  are  borne. 

Conidium  (dust).  An  asexual  spore  of  a  fungus,  generally  formed  in  the 
air. 

Coniferous.    Cone  bearing. 


244  GLOSSARY 

Conjugation.  The  sexual  union  of  similar  gametes  to  form  a  zygospore 
or  zygote. 

Cork.    Protective  tissue  in  the  outer  portions  of  the  bark. 

Corm  (a  trunk).    The  bulb-like  fleshy  base  of  some  stems. 

Corolla  (a  small  crown).  A  collective  term  for  the  petals  or  inner  mem- 
bers of  the  perianth. 

Cortex.    The  bark  or  rind. 

Cotyledon.    An  embryo  leaf  borne  by  the  hypocotyl. 

Cuticle  (the  outer  skin).    The  exterior  layer  of  the  epidermis. 

Cystocarp  (bladder  fruit).  The  fruit  of  the  red  algse  resulting  from  the 
fertilization  of  the  carpogonium. 

Cytoplasm  (cell  plasm).  The  general  protoplasm  of  the  cell  exclusive  of 
the  nucleus  and  plastids. 

Deciduous  (to  fall).    Falling  when  their  function  is  performed,  as  the 

leaves  of  most  hard-wood  trees  in  temperate  climates. 
Dehiscent  (to  yawn).    Opening  spontaneously  when  mature,  as  anthers, 

to  discharge  pollen,  or  as  capsules,  to  discharge  spores. 
Dermatogen  (skin  producer).    The  layer  of  cells  around  growing  points 

from  which  the  epidermis  is  derived. 
Determinate.    A  term   applied  to  stems  where  the  growth  in  length  is 

determined  by  the  presence  of  a  winter  bud,  and  to  an  inflorescence 

where  there  is  a  terminal  flower  bud. 
Diageotropic.    Growing  horizontally  under  the  influence  of  gravity,  as 

some  branches  do. 
Dicotyledonous.    Having  two  seed  leaves  or  cotyledons. 
Dimorphous  flowers  (two  forms).    Flowers  which  have  two  forms,  as  long 

and  short  styled. 
Dioecious    (two    households).    Unisexual,   the   male  and   female  sexual 

organs  borne  by  separate  individuals. 
Dorsiventral  (back,  belly).    Having  upper  and  lower  faces,  as  in  most 

leaves. 
Drupe  (an  olive).    A  stone  fruit,  as  a  peach  or  plum. 

Ecology  (household  discourse).  The  study  of  plants  in  relation  to  their 
surroundings.  The  term  is  often  rnade  to  include  much  of  the 
subject-matter  of  ecological  plant  geography,  or  the  distribution  of 
plants  on  the  earth  with  reference  to  environment.  In  this  sense 
it  is  very  frequently  used  in  connection  with  the  study  of  plant 
formations. 

Egg.  A  nonmotile  female  gamete,  generally  large  in  comparison  with 
the  sperm. 

Egg  apparatus.  A  group  of  three  cells  at  the  micropylar  end  of  the 
embrj^o  sac,  consisting  of  the  egg  and  two  synergids. 

Elater  (a  driver).  A  spirally  thickened  elongated  cell  or  other  filamen- 
tous structure  developed  to  assist  in  expelling  spores  from  a  spore 


GLOSSARY  245 

Embryo  (a  rudimentary  animal).    The  nidimontary  plantlct,  as  in   the 

seed. 
Embryo  sac.    The  cavity  which  contains  Mic   female  ^ametopliytc  f»f  a 

seed  plant  and  later  the  embryo  and  cn(los)M'rm  (if  present)  in  tin- 

seed. 
Emergence.    An  outgrowth  from  the  surface  of  a  plant  not  (like  a  hair) 

arising  solely  from  the  epidermis  nor  (like  a  thorn)  from  a  i»ud. 
Endosperm  (within  the  seed).    A  parenchymatous  tissue  formed  within 

the  embryo   sac  and  often  developed    into  the  princi}»al    mass   of 

reserve  material  in  the  seed. 
Entomophilous  (insect  loving).    A  term  applied  to  i)lants  that  are  ]»ol- 

linated  by  insects. 
Enzyme  (in  yeast).    An  unorganized  or  soluble  ferment  (such  as  dias- 
tase) which  is  not  associated  with  any  organism. 
Epidermis  (upon  the  skin).    The  cellular  skin  or  covering  of  the  plant 

body  inside  the  cuticle. 
Epigynous.    A  term  applied  to  flowers  in  which  the  stamens  and  perianth 

appear  to  grow  from  the  top  of  the  ovary. 
Epiphyte  (upon  a  plant).    A  plant  which  grows  upon  other  jilants  but 

not  parasitically,  —  an  air  plant. 
Eusporangiate.    A  term  applied  to  pteridophytes  the  sporangia  of  which 

arise  from  a  group  of  cells. 

Family.    A  taxonomic  group  standing  between  genus  and  order. 

Fertilization.  The  fusion  of  two  sexual  cells,  especially  the  fusion  of  the 
sperm  with  the  egg. 

Fiber.    A  slender,  thick-w^alled  cell,  many  times  longer  than  its  width. 

Fibro-vascular.    Composed  of  fibers  and  vessels,  as  a  fibro-vascular  bundle. 

Filament  (a  thread).    The  stalk  of  a  stamen  bearing  the  anther. 

Fission.  The  process  of  cell  division  by  a  gradual  ])inching  in  two  of 
the  cell. 

Flower.  An  assemblage  of  organs  in  the  seed  plants  necessary  for  ferti- 
lization, often  with  protecting  envelo})es.  The  flower  of  the  angii)- 
sperms  when  bisexual  usually  consists  of  a  perianth,  stamens,  ami 
pistil  or  pistils. 

Foot.  A  portion  of  the  sporophyte  set  apart  to  absorb  water  or  nourish- 
ment from  the  gametophyte. 

Formation.  An  ecological  term  denoting  a  well-defined  assemblage  ot 
plants  characteristic  of  a  given  kind  of  station,  as  a  peat  bog. 

Frond  (a  leaf).  The  leaf  of  a  fern,  generally  both  vegetative  and  spore 
producing  in  its  functions. 

Fruit.  The  ripened  seed  case  and  its  contents,  or,  in  a  broader  sense,  a 
spore-producing  structure  of  the  lower  plants. 

Fundamental  tissue.  The  general  ground  tissue  (mostly  unditTerentiated) 
in  wdiich  fibro-vascular  bundles  and  t)ther  specialized  tissues  arise. 

Funiculus  (a  little  rope).  The  stalk  by  which  the  ovule  or  seed  is  at- 
tached to  the  placenta. 


246  GLOSSARY 

Gametangium  (gamete  vessel).    The  organ  which  produces  gametes. 
Gamete.    A  sexual   reproductive  cell  which  ordinarily  must  fuse  with 

another  gamete  in  order  to  live. 
Gametophjrte  (gamete  plant).    The  sexual  plant  in   an    alternation  of 

generations,  producing  sexual  cells  or  gametes  (see  Sporophyte). 
Gemma,  plu.  gemmcB  (a  bud).    An  asexual  reproductive  body,  generally 

many  celled,  rather  characteristic  of  the  bryophytes. 
Generative  cell.    The  cell  within  the  male  gametophyte  of  seed  plants 

from  which  the  two  sperm  nuclei  are  developed. 
Genus,  plu.  genera  (a  race).    The  taxonomic  group  composed  of  related 

species. 
Geotropism  (earth  turning).    The  action  of  gravity  in  directing  growth. 
Gill.    A  flat  spore-bearing  plate  on  the  under  side  of  a  mushroom  or  toad- 
stool. 
Glume  (a  husk).    A  chaffy  bract  on  the  inflorescence  of  grasses. 
Grain.    Such  a  seed-like  fruit  as  that  of  the  grasses,  —  a  minute,  roundish 

body,  as  a  starch  grain. 
Ground  tissue.    See  fundamental  tissue. 
Growing  point.    The  meristematic  tip  of  the  root  or  stem  from  which 

the  tissues  are  produced. 
Guard  cell.    One  of  the  cells  (usually  two  in  number)  which  serve  to 

open  and  close  a  stoma. 
Gymnosperms  (naked  seeds).    Plants  (as  the  Coniferce)  which  have  no 

closed  ovaries,  so  that  the  seeds  are  borne  naked,  usually  on  scales. 

Halophyte  (salt  plant).  A  plant  which  habitually  grows  in  saline  soils, 
as  on  sea  beaches  or  in  salt  marshes. 

Haustorium  (a  drawer).  A  sucker-like  absorbing  organ  of  a  parasitic 
plant. 

Heliotropism  (sun  turning).    The  action  of  light  in  directing  growth. 

Hermaphrodite.  Having  both  forms  of  sexual  organs  together  in  the 
same  structure ;  bisexual. 

Heterocyst  (unlike  cell).  In  the  blue-green  algre  a  large  cell,  empty  or 
almost  empty  of  protoplasm. 

Heterogamy  (unlike  gametes).  The  condition  where  the  pairing  gametes 
are  different  in  form  and  structure,  as  the  Qgg  and  sperm. 

Heterospory  (unlike  spores).  The  condition  in  which  a  sporophyte  pro- 
duces spores  of  two  sizes,  microspores  and  megaspores. 

Hilum.  The  scar  on  a  seed  showing  its  point  of  attachment  to  the 
funiculus  or  the  placenta. 

Holdfast.    An  organ  of  attachment  developed  by  certain  algae. 

Homologous  (similar  discourse).  Of  one  type,  though  differing  in  form 
and  function. 

Homospory  (similar  spores).  The  condition  in  which  a  sporophyte  pro- 
duces spores  of  the  same  size. 

Hormogonium  (chain  offspring).  A  portion  of  the  filament  of  a  blue-green 
alga  reproductive  in  function. 


GLOSSARY  247 

Host.    A  plant  or  animal  wliich  nourishes  a  ])avasit,f"'. 

Hybrid  (a  mongrel).  The  offspring  ol»t,aine«l  l»y  the  artion  of  th«'  pollen 
of  one  species  on  the  pistil  of  another.  The  term  is  also  used  for 
tlie  offspring  of  any  cross. 

Hydrophyte  (water  plant).    A  water  plant. 

Hygroscopic  (moisture  seeing).  Expanding  or  shrinking  rea<lily  under 
the  influence  of  moisture. 

Hymenium  (a  membrane).    An  expanded  fruiting  surface  of  a  fungus. 

Hypha,  plu.  hi/phce  (a  web).    The  filament  of  a  fungus. 

Hypocotyl.  The  portion  of  an  embryo  or  very  young  seedling  between 
the  cotyledons  and  the  root. 

Hypogynous.  A  term  applied  to  flowers  in  which  the  stamens  and  peri- 
anth grow  from  beneath  the  ovary. 

Indeterminate.    A  term  applied  to  stems  where  the  growth  in  length  is 

indefinite  because  no  terminal  bud  is  formed,  and  to  an  inflorescence 

where  there  is  no  terminal  flower. 
Indusium.    In  ferns  a  protective  outgrowth   from  the  leaf  covering  a 

cluster  of  sporangia  or  sorus. 
Inferior  ovary.    See  Epigynous. 
Inflorescence  (flowering).    The  manner  in  which  the  flowers  are  arranged 

in  the  flower  cluster. 
Intercellular.    Between  the  cells  or  among  them. 
Internode.    The  portion  of  the  stem  between  two  nodes. 
Involucre  (a  wrapper).    A  ring  of  bracts  surrounding  several  flowers  (ir 

their  flower  stalks. 
Irritability  (easily  excited).    Sensitiveness  to  stimuli,  such  as  light,  heat, 

gravity,  etc. 
Isogamy  (equal  gametes).    The  condition  where  the  pairing  gametes  are 

similar  in  form  and  structure. 

Lamina,  plu.  lamincc  (a  layer).    The  blade  of  a  leaf. 

Leaf  trace.    The   group  of   fibro-vascular  bundles  which   connects   the 

veins  of  the  leaf  with  the  fibro-vascular  system  of  the  stem. 
Lenticel.    A  roundish  or  lens-shaped  spot  on  young  bark,  nuirking  the 

former  position  of  a  stoma. 
Leptosporangiate.    A  term  applied  to  pteridophytes  in  which  the  s]>oran- 

giuni  arises  from  a  single  epidermal  cell. 
Leucoplast  (white  molded).    A  protoplasmic  body  found  in  oflis  in  the 

interior  of  the  plant  body,  often  serving  as  a  starch  builder,  —  a 

colorless  plastid. 
Lignin  (wood).    The  thickening  material  deposited  in  cell  walls  to  j)rcv 

duce  woody  tissue. 
Locule  (a  little  compartment).    A  cavity  or  chamber,  as  of  an  dvary. 

Medullary  (belonging  to  the  marrow).  Related  to  the  pith,  as  the  med- 
ullary rays. 


248  GLOSSARY 

Megasporangium  (large  spore  vessel).  The  sporangium  which  develops 
megaspores, 

Megaspore  (large  spore).  The  larger  one  of  the  two  sorts  of  spores  pro- 
duced by  heterosporous  pteridophytes ;  it  gives  rise  to  a  female 
gametophyte. 

Megasporophyll  (large  spore  leaf).    A  leaf  bearing  megaspores. 

Meristem  (divisible).  Formative,  rapidly  dividing  tissue  such  as  cam- 
bium or  the  cells  of  growing  points. 

Mesophyll  (middle  leaf).  The  entire  parenchyma  of  the  leaf,  inside  the 
epidermis. 

Mesophyte.  A  plant  adapted  to  live  with  a  moderate  amount  of  soil 
water  and  humidity. 

Micropyle  (small  gate).  The  small  opening  between  the  integuments 
leading  to  the  nucellus  of  an  ovule. 

Microsporangium  (small  spore  vessel).  A  sporangium  which  develops 
microspores. 

Microspore  (small  spore).  The  smaller  of  the  two  sorts  of  spores  pro- 
duced by  heterosporous  pteridophytes ;  it  gives  rise  to  a  male 
gametophyte. 

Microsporophyll  (small  spore  leaf).    A  leaf  bearing  microspores. 

Mitosis  (a  thread  or  web).  The  process  of  indirect  nuclear  division 
characterized  by  the  presence  of  a  spindle. 

Monocotyledonous.    Having  only  one  seed  leaf  or  cotyledon. 

Monoecious  (one  household).  Having  the  male  and  female  sexual  organs 
borne  separately  by  the  same  individual. 

Morphology  (form  discourse).  The  science  of  the  form  and  structure  of 
an  organism. 

Mutation.  A  decided  and  abrupt  departure  in  the  offspring  from  the 
characters  of  the  parent,  often  sufficient  to  constitute  a  new  species. 

Mycelium  (fungus  growth).  A  mass  of  vegetative  fungal  filaments,  or 
hyphse. 

Nastic.  A  term  applied  to  movements  produced  by  all-round  (not  one- 
sided) stimuli.  The  opening  and  closing  of  such  flowers  as  the  cro- 
cus, tulip,  etc.,  are  thermonastic  movements. 

Nectary.    The  organ  in  which  nectar  is  secreted. 

Node  (a  knot).  The  part  of  a  stem  which  normally  bears  a  leaf  or  group 
of  leaves. 

Nucellus  (a  little  kernel).  The  portion  of  the  ovule  within  the  integu- 
ments and  containing  the  embryo  sac. 

Nucleolus  (diminutive  of  nucleus).  A  small  readily  stained  body,  gen- 
erally present  with  the  chromatin,  in  the  nucleus ;  also  called  a 
nucleole. 

Nucleus  (a  kernel).  The  organ  of  the  cell  containing  the  chromatin  and 
nucleolus. 

Oogonium  (egg  offspring).  The  cell  in  the  thallophytes  which  develops 
the  egg  ;  also  called  an  oogone. 


GLOSSARY  249 

Oosphere  (egg  sphere).    An  egg  cell. 

Oospore  (egg  spore).    A  fertilized  o.gg  which  develops  a  heavy  w;ill  and 

passes  through  a  [leriod  of  rest  before  gerniinaling. 
Open  bundle.    A  Hbro-vascular  bundle  which  contains  cambiiini  and  's 

consecpiently  capable  of  further  growth. 
Operculum,  plu.  opercula  (a  cover).    In  mosses  the  cover  of  the  spore  case. 
Order.    A  taxononiic  group  composed  of  families. 
Osmosis  (a  thrusting).    The  diffusion  or  interchange  of  licjuids  through 

membranes. 
Ovary.    The  ovule-bearing  part  of  the  pistil. 
Ovule.    The  undeveloped  structure  which  after  fertilization  becomes  the 

seed. 

Palisade  cells.    Elongated  parenchyma  cells  of  a  leaf,  which  lie  beneatl 

the  epidermis  with  their  long  axes  at  right  angles  to  the  leaf  surface 
Palmate  (like  the  palm  of  the  hand).    AVith  veins  or  sinuses  radiating 

like  fingers. 
Parasite.    An  animal  or  plant  that  obtains  its  food  from  some  other  liv- 
ing organism,  called  its  host. 
Parenchyma.    Tissue  composed  of  nearly  globular  cells  or  polyhedral 

cells  the  diameters  of  which  are  approximately  equal,  as  pitli. 
Parietal  (a  house  wall).    Pertaining  to  a  wall,  as  a  placenta  on  an  ovary 

wall. 
Parthenogenesis   (virgin   generation).    The  development  of  an  i^gg  or 

other  gamete  without  the  process  of  fertilization. 
Pathogenic  (disease  offspring).    Producing  disease. 
Pedicel  (a  little  foot).    The  stalk  on  which  an  organ  is  borne,  esjiecially 

the  flower  stalk  of  each  separate  flower  in  a  cluster. 
Peduncle  (a  little  foot).    The  flower  stalk. 
Perianth  (around  the  flower).    A  collective  term  for  calyx  and  corolla 

taken  together. 
Periblem  (clothing).    The  part  of  the  meristem  at  the  growing  apex  of 

a  root  or  shoot,  immediately  beneath   the  epidermis.     It  develops 

into  the  cortex. 
Pericambium.    See  Pericycle. 

Pericycle.    The  outermost  layer  of  the  central  cylinder  of  a  root. 
Perigynous.    A  term  applied  to  those  flowers  in  which  the  stamens  and 

perianth  appear  to  grow  from  around  the  wall  of  the  ovary. 
Peristome  (around  the  mouth).    In  mosses  the  circle  of  teeth  or  .segmenta 

surrounding  the  opening  of  the  spore  case. 
Perithecium   (around    a    case).      In    sac    fungi,    Ascomycctcs  (including 

lichens),  a  cavity  containing  the  sacs  or  asci. 
Petal  (a  flower  leaf).    A  leaf  of  the  corolla. 
Petiole  (a  little  foot).    A  leaf  stalk. 
Phloem  (bark).    The  soft  portion  of  a  fibro-vascular  bundle,  —  the  bast. 

In  dicotyledons  the  part  outside  of  the  cand)ium,  —  the  inner  i>ark. 
Photosynthesis  (light  putting  together).    Th«'  process  of  manufacture  of 

carbohydrates,  such   as  starch    and    sugar,   fnun    water   antl   carbon 


250  GLOSSARY 

dioxi(l(\  Tt  is  cavricd  on  l>y  the  cliromatophores  and  chloroplasts 
acted  on  l)y  the  energy  of  snnlight. 

Physiology.    The  science  of  tlie  action  and  fnnctions  of  organisms. 

Pinnate  (a  feather).  Having  leaflets  arranged  along  two  sides  of  a  main 
leaf  axis. 

Pistil  (a  pestle).  The  simple  or  componnd  structure  (composed  of  one 
or  more  carpels)  which  in  angiosperms  contains  the  ovules. 

Placenta.    The  ovule-bearing  portion  of  the  interior  of  the  ovary. 

Plageotropic  (oblique  turning).  Assuming  an  oblique  direction  under 
the  influence  of  gravity,  as  most  secondary  roots. 

Plasma  membrane.    The  limiting  membrane  of  a  protoplast. 

Plasmolysis  (that  w^hich  is  formed,  loosing).  A  separation  by  osmotic 
action  of  the  protoplast  from  the  cell  wall. 

Plastid  (that  formed).  A  protoplasmic  body  usually  with  a  special  func- 
tion. The  term  is  used  collectively  for  chloroplasts,  chromoplasts, 
and  leucoplasts. 

Plerome  (that  which  fills).  That  part  of  the  meristem  near  a  growing 
point  wdiich  is  surrounded  by  the  periblem  and  develops  into  the 
central  cylinder. 

Plumule  (a  little  feather).  The  primary  leaf  bud  of  an  embryo  seed 
plant. 

Pod.    A  dry,  many-seeded,  dehiscent  fruit. 

Pollen  (fine  flour).  Minute  grains  developed  in  the  pollen  mother  cells 
of  the  anther  and  essential  for  the  fertilization  of  the  ovule.  The 
locules  of  the  anther  are  morphologically  microsporangia  and  the 
pollen  grains  are  microspores. 

Pollen  tube.  The  structure  which  is  developed  from  the  inner  coat  of  the 
pollen  grain  and  serves  to  carry  the  sperm  nuclei  into  the  embryo 
sac  of  the  ovule. 

Pollination.  The  transference  of  the  pollen  to  the  stigma  or  to  the 
naked  ovule  of  the  gymnosperms. 

Prosenchyma.    Tissue  composed  of  elongated  cells. 

Proteid.  Any  one  of  a  group  of  nitrogenous  compounds  of  which  albu- 
men is  an  example. 

Prothallium  (before  a  young  shoot).  The  gametophyte  developed  from 
the  spore  of  a  pteridophyte. 

Protonema,  plu.  protonemata  (first  thread).  A  filamentous  growth  devel- 
oped from  the  spore  of  a  moss,  from  which  the  leafy  moss  plants 
arise.  ' 

Protoplasm  (first  formed).  The  living  part  of  the  material  of  the  plant 
or  animal  body  contained  in  the  cells. 

Protoplast.  A  unit  of  protoplasm,  or  cell,  with  or  without  a  cell 
wall. 

Pteridophytes  (fern  plants).  The  great  group  composed  of  the  ferns, 
horsetails,  and  club  mosses. 

Pyrenoid  (resembling  a  kernel).  Minute  bodies  imbedded  in  the  cliro- 
matophores, which  act  as  centers  of  starch  formation. 


GLOSSARY  251 

Receptacle.  The  extremity  of  the  flower  stalk,  on  which  tin-  floral  parts 
are  borne ;  in  (.'oiuposltte  the  cojiimon  receptacle  hears  the  head  of 
flowers,  —  any  .structure  carrying  sexual  organs. 

Rhizoid  (reseniMing  a  root).    A  root-like  filament  in  the  lower  plants. 

Rootstock.  A  somewhat  root-like  stem,  usually  nearly  horizontal  and 
dorsiventral,  extending  either  above  or  under  ground. 

Saprophyte  (rotten  plant).    A  plant  that  lives  on  dead  organic  matter. 

Scape  (a  stem).    A  leafless  peduncle  arising  from  the  ground. 

Sclereid  (hard).    See  Stone  cell. 

Sclerenchyma.  Rigid  or  strengthening  tissue,  composed  of  thick-walled 
cells,  often  having  the  form  of  fibers. 

Secondary  growth.  Tlie  growth  w hich  takes  place  in  gymnos]»erms  and 
woody  dicotyledons  from  the  development  of  the  cambium  cylinder. 

Seed.    The  fertilized  and  matured  ovule. 

Seed  plant.  A  member  of  the  highest  division  of  the  plant  king<l«»m, 
characterized  by  producing  seeds. 

Sepal  (a  covering).    A  leaf  of  the  calyx. 

Sieve  tubes,  or  Sieve  cells.  Soft  bast  or  phloem  cells  with  ] perforated 
sieve  platen  in  their  walls. 

Species.  A  kind  of  plant  or  animal,  one  of  the  taxonomic  subdivisions 
of  a  genus. 

Sperm.  A  male  gamete,  generally  very  small  and  motile  in  comparison 
with  the  eg^. 

Spermatia.    Non-motile  sperms,  as  in  the  red  algae. 

Spermatophytes  (seed  plants).  The  great  group  composed  of  seed 
plants. 

Spermogonium.  In  the  rusts  a  cup-shaped  receptacle  ]>roduciug  minute 
cells  (spermatia)  believed  to  be  sjierms  no  longer  functional. 

Spindle.  A  mechanism  consisting  of  delicate  fibrils  concerned  witli  the 
distribution  of  the  chromosomes  during  nuclear  division  (mitosis). 

Sporangium  (spore  vessel).    A  spore-producing  case. 

Spore  (seed).  A  term  ai)plied  to  a  variety  of  one-  or  few-celled  repri>- 
ductive  bodies  characteristic  of  groups  below  the  seed  ]tlants. 

Sporidium  (diminutive  of  spore).    A  spore  produced  by  a  jtromycelium. 

Sporogonium  (spore  offspring).  The  sporophyte  generation  of  the  liver- 
worts and  mosses,  sometimes  called  the  fruit. 

Sporophyll  (spore  leaf).    A  leaf  which  bears  spores. 

Sporophyte  (spore  plant).  The  asexual  })lant  in  an  alternation  of  gen- 
erations producing  asexual  spores  (see  gameto}>hyte). 

Stamen.  The  pollen-bearing  organ  of  seed  j^lants  ;  morphologically  a 
microsporophyll. 

Stele  (a  pillar).  The  central  cylinder  of  a  stem  or  root.  Sometimes  a 
stem  has  more  than  one  plerome  strand  at  the  growing  point  and  so 
develops  several  cylinders  and  is  called  polj/stelir. 

Stigma  (a  spot  or  mark).  The  portion  of  the  pistil  (destitute  of  epider- 
mis) on  which  the  pollen  lodges  and  germinates. 


252  GLOSSARY 

Stoma,  plu.  stomata  (a  mouth).    An  opening  through  the  leaf  epidermis 

which  serves  for  transpiration.    The  stomatic  apparatus  consists  of  the 

stoma  and  its  guard  cells. 
Stone  cell.    A  hard  cell  with   its  walls  much  thickened  by  secondary 

deposits,  as  the  grit  cells  of  the  pear. 
Strobilus  (a  fir  cone).    A  cone-like  cluster  of  sporophylls. 
Style  (a  pillar).    An  elongation  of  the  pistil  above  the  ovary,  bearing 

the  stigma. 
Suspensor.    In  seed  plants  and  club  mosses  a  structure  arising  from  the 

fertilized  egg,  which  pushes  the  developing  embryo  deep  into  the 

tissue  of  the  gametophyte  or  endosperm. 
Symbiont.    An  organism  living  in  a  condition  of  symbiosis. 
Symbiosis  (living  together).  The  condition  in  which  two  or  more  organ- 
isms are  living  in  intimate  physiological  relationship. 
Sympetalous.    AVith  the  petals  appearing  as  if  grown  together  by  their 

edges. 
Synergids  (co-workers).    Two  cells  accompanying  the  egg  at  the  micro- 

pylar  end  of  the  embryo  sac,  the  group  of  three  constituting  the  egg 

apparatus. 
Synsepalous.    With  the  sepals  appearing  as  if  grown  together  by  their 

edges. 

Taxonomy  (order,  law).    The  study  of  classification.    Plant  taxonomy 

is  often  called  systematic  botany. 
Teleutospores  (end  spores).    The  resting  spores  (chlamydospores)  of  the 

rusts,  producing  a  promycelium. 
Testa  (a  shell).    The  outer  coat  of  the  seed. 
Tetraspore  (four  spore).    An  asexual  spore  characteristic  of  the  red  algae, 

usually  produced  in  groups  of  four. 
Thallophytes  (thallus  plants).   The  great  group  composed  of  the  algae 

and  fungi. 
Thallus  (a  young  shoot).    A  simple  vegetative  body  without  differentia- 
tion into  roots,  stem,  or  leaves. 
Tissue.    A  definite  region  of  similar  cells  with  the  same  functions. 
Trachea,  plu.  trachece  (the  windpipe).    See  Vessel, 
Tracheid  (trachea-like).    An  elongated  cell  with  closed  ends  and  the  walls 

with  secondary  thickening,  as  the  pitted  cells  of  coniferous  wood. 
Trichogyne.    A  delicate  filamentous  extension  from  the  carpogonium, 

specialized  to  receive  the  sperms. 
Tropophyte.    A  plant  which  is  mesophytic  during  part  of  the  year  and 

xerophytic  during  the  remaining  part,  as  most  deciduous  trees. 
Turgor.    The  inflated  or  distended  condition  of  a  cell  which  is  full  of 

liquid. 

Unisexual.    Having  only  male  or  female  reproductive  organs. 
Uredospore  (blight  spore).    A  spore  of  the  rusts  for  rapid  multiplication 
(summer  spore). 


GLOSSARY  263 

Variety.    A  subdivision  of  a  species. 

Vein.    A  fibro-vasciilar  bundle  of  a  leaf,  petal,  or  other  thin  anrl  flat 

organ. 
Venation.    The  manner  in  which  veins  are  distributed. 
Venter.    The  swollen  basal  portion  of  an  archegonium  containing  the  egg. 
Vernation.    The  manner  of  unfolding  in  buds. 
Vessel.    A  tube  or  duct  made  of  separate  sections  but  continuous  from 

the   absorption   of  the   cross  partitions.     The   walls    have    various 

thickening  deposits,  often  spiral  or  ring-formed. 
Volva  (a  wrapper).    An  envelope  inclosing  a  young  toadstool  and  ruj>- 

tured  by  the  growth  of  the  latter,  portions  sometimes  remaining  as 

scales  on  the  top  of  the  cap  and  sometimes  as  a  cup  at  the  base  of 

the  stalk. 

Xeroph3i;e  (dry  plant).    A  plant  which  can  live  with  a  scanty  supply  of 

water. 
Xylem  (wood).    The  wood  or  inner  part  of  a  fibro-vascular  bundle,  the 

portion  within  the  bundle  cambium. 

Zone.    In  ecology  a  band  of  any  given  plant  formation,  usually  bounded 

by  other  bands  representing  other  formations,  as  about  a  pond,  a 

salt  spring,  etc. 
Zoospore  (animal  spore).    A  ciliated  and  therefore  motile  asexual  spore. 
Zygomorphism  (yoke  form).    The  arrangement  of  parts  in  corresponding 

light  and  left  halves  ;  bilateral  symmetry. 
Zygospore  (yoke  spore).    A  sexually  formed  spore  resulting  from  the 

fusion  of  similar  gametes  (isogamy)  ;  also  called  a  zygote. 


INDEX 


A. corn,  71 

.\gariciis,  type  study,  IK),  117 
Albugo,  typo  study,  101) 
Alcohol  as  a  preservative,  1U5,  196 
Aleurone  grains,  27 
Algae,  culture  of,  211,  212 
Amoeba,  type  study,  80 
Anabaena,  type  study,  80 
Anthoceros,  type  study,  125 
Apparatus,  dealers  in,  225,  22() 
Apparatus  for  the  laboratory,  222, 

223 
Aspergillus,  type  study,  111,  112 

Bacteria,  culture  of,  102-104 

Bacteria,  type  study,  104,  105 

BalsarQ,  mounting  in,  200,  201 

Basidia  fungi,  field  work  on,  110 

Bean  pod,  69,  70 

Bean  seed,  18,  19 

Bleaching  after  osmic  acid,  208 

Blue-green  algcB,  held  work  on,  84 

Bread  mold,  type  study,  107,  108 

Buds,  48-50 

Buttercup  flower,  67,  68 

Capsella,    development   of    embryo, 

165 
Capsella,  development  of  flower,  164 
Capsella,  development  of  ovule,  164, 

165 
Caraway  fruit,  70 
Carnivorous  plants,  167,  168 
Carnoy's  fluid,  195 
Cell  division,  study  of,  81,  82,  160, 

161 
Cellulose,  23 
Cliara,  type  study,  96 
Charts,  7,  226 
Chemical     compounds     in     plants, 

rect)gnition  of,  23,  24 
Chemicals  for  the  l.iboratory,  224 
Cherry  fruit,  73 


Chrom-acetic  acid,  191-103 

Chrom-osmo-acetic  acid,  193,  194 

Cladophora,  type  study,  91 

Classes,  ecological,  175 

Club  mosses,  held  work  (»n.  132.  13:5 

Coleochiete,  tyijc  study,  92 

Competition  among  plants,  174 

Composite,  type  study,  186,  187 

Convallaria,  type  study,  179,  180 

Cork,  42,  47 

Corn  grain,  19,  22,  23 

Corn  stem,  39,  40 

Cycad,  type  study,  151 

Dehydration,  203 

DelafieUrs     lux'matoxyliu,     staining 

with,   1<)8,  199,  200 
Desmids,  type  study,  93 
Diatoms,  type  study,  94 
Dock  fruit,  70,  71 

Ectocarpus,  type  study,  97 

Elder,  study  of  male  gametophvf*'. 

163,   1(54 
Elm  leaf,  51 

Eosin,  staining  with,  197 
iMjuisetum,  type  study,  142-145 
Erigeron,  tyi)e  study,  187 
Erythronium,  type  study,  IHO,  isi 
Erythrosin,  sUiining  with,  200,  210 
Euglena,  type  study,  Sii 

Fern,  type  study,  13:^-139 
Ferns,  culture  of,  216 
Ferns,  held  work  on.  132,  i:i3 
Ficus  elastica  leaf,  5(5,  (51,  62 
Fixini;,  191-195 
FIciMMiing's  lluids,  193,  194 
Flower  of  angiospoi-nis,  64-()8 
Formalin  as  a  lueservative,  190 
Fiuit  of  angiospcnns,  (59-74 
Fruit  of  angiosperms,  development 
of,  73,  74  ■ 


256 


INDEX 


Fuchsin,   acid,   staining  with,   199, 

210 
Fucus,  type  study,  98,  99 
Funaria,  type  study,  127-132 
Fungi,  culture  of,  212-214 

Gentian  violet,  staining  with,  209 
Germination  of  seeds,  17-21 
Gill  fungus,  type  study,  116,  117 
Gloeocapsa,  type  study,  84 
Glycerin,  mounting  in,  201,  202 
Glycerin  jelly,  mounting  in,  202 
Green  algae,  field  work  on,  87 
Growing  point  of  stem,  50,  51 

Halophytes,  176,  177 
Hanging-drop  cultures,  214 
Heliotropic  movements,  54,  55 
Horse-chestnut  seed,  19 
Horsetails,  field  work  on,  132,  133 
Hydrodictyon,  type  study,  89 
Hydrophytes,  175,  176 

Imbedding  in  paraffin,  202-204 
Invasion  among  plants,  174,  175 
Iron-alum     hgematoxylin,     staining 

with,  197,  198,  208 
Iron-alum    hsematoxylin    and    saf- 

ranin,  staining  with,  208,  209 
Isoetes,  type  study,  150,  151 

Killing,  191-195 
Knop's  solution,  211,  212 

Lantern  slides,  7,  226 

Lathyrus,  type  study,  184 

Leaves,  51-63 

Leguminosse,  type  study,  183,  184 

Lemon  fruit,  71-73 

Lichen,  type  study,  112,  113 

Lignin,  23,  24 

Liliacese,  type  study,  179-181 

Lily,  development  of  embryo  sac, 
162 

Lily,  development  of  endosperm,  163 

Lily,  development  of  pollen,  160, 161 

Lily,  fertilization  and  double  fertili- 
zation, 163 

Lily  leaf,  55,  56 

Liverworts,  culture  of,  216 

Liverworts,  field  work  on,  117,  118 

Lycopodium,  type  study,  145,  146 


Maple  leaf,  52 

Marchantia,  type  study,  119-123 
Marine  alga?,  field  work  on,  97 
JVIarsilia,  type  study,  139-142 
Material,  dealers  in,  225,  226 
Material  for  plant  histology,  220-222 
Material,  preservation  of,  195,  196 

Mesophytes,  175,  176 

Methyl  green,  staining  with,  200,  21G 

Microscope,  compound,  construction 

of,  10,  11 
Microscope,  compound,  use  of,  12-14 
Microsphsera,  tjrpe  study,  110,  111 
Mineral  constituents  of  plants,  33,  34 
Mitosis,  study  of,  81,  82,  160,  161 
Moore's  solution,  212 
Moss,  type  study,  127-132 
Moss  leaf,  cell  structure  of,  80 
Mosses,  culture  of,  215 
Mosses,  field  work  on,  117,  118 

Nastic  movements  of  leaves,  53,  54 
Nemalion,  type  study,  100,  101 
Nitella,  type  study,  96 
Nocturnal  position,  53 
Nostoc,  type  study,  86 
Nuclear  division,  study  of,  81,  82, 
160,  161 

(Edogonium,  type  study,  91,  92 

Oil,  24-26 

Onion,  47,  48 

Orange  G,  staining  with,  209 

Oscillatoria,  type  study,  85 

Osmosis,  36,  37,  77 

Oxygen  making,  57 

Parasites,  167 
Pea  seed,  19 

Penicillium,  type  study.  111,  112 
Peziza,  type  study,  112 
Physcia,  type  study,  112,  113 
Pine,  type  study,  151-159 
Plasmodium,  type  study,  84 
Plasmolysis  in  Spirogyra,  77 
Pleurococcus,  type  study,  87,  88 
Pollen  tubes,  68,  69 
Pollination,  169-172 
Polysiphonia,  type  study,  101,  102 
Pond  scums,  type  study,  93 
Porella,  type  study,  123-125 


INDEX 


257 


Potato  agar,  cultures  on,  213,  214 
Potato  tuber,  46,  47 
Propagation  by  roots,  30 
Propagation,  vegetative,  172,  173 
Protection  of  plants  from  animals, 

168 
Proteids,  24,  26,  27 
Prothallia,  culture  of,  216 
Protonema,  culture  of,  216 
Protoplasm,  circulation  of,  81 
Prunus,  type  study,  182,  183 
Puccinia,  type  study,  114,  115 

Ranunculacese,  type  study,  181 
Reagents,  general,  188,  189 
Reagents,  special,  190,  191 
Rhizopus,  type  study,  107,  108 
Ricciocarpus,  type  study,  118 
Robinia,  type  study,  183,  184 
Root,  28-33 

Roots,  physiology  of,  34-37 
Rosa,  type  study,  181,  182 
Rosaceae,  type  study,  181-183 

Sac  fungi,  field  work  on,  110 
Safranin,  staining  w^itli,  199,  209 
Safranin  and  Delafield's  hfematoxy- 

lin,  staining  with,  199,  210 
Safranin,  gentian  violet,  and  orange 

G,  staining  with,  209 
Saprolegnia,  type  study,  108 
Secondary  growth  of  stem,  43,  44 
Sectioning  in  paraffin,  205-207 
Sectioning  free-hand,  204,  205 
Seed  plants,  culture  of,  216 
Seeds,  dissemination  of,  173,  174 
Selaginella,  type  study,  146-150 
Shade  leaves,  55 
Slides  for  histology  of  seed  plants, 

219 
Slides  for  study  of  plant  cell,  217 
Slides  for  type  studies,  217-219 
Slime  mold,  type  study,  83,  84 
Smut,  type  study,  114 
Sphgerella,  type  study,  88 
Sphagnum,  type  study,  126 
Spirogyra,  cell  structure  of,  75-77 
Spirogyra,  zygospore  formation,  78, 

79 
Sporodinia,  type  study,  108 
Squash  seed,  17,  18 


Staining  in  bulk,  197-200 
Staining  on  the  slide,  207-210 
Starclj,  23-25,  iW,  47,  57-59,  63 
Starch  in  leaves,  57-59 
Stem,  dicotyledonous,  structure  of, 

41-44 
Stem,  monocotyledonous,  structure 

of,  39,  40 
Stem,  work  of,  45-48 
Storage  of  food  in  seeds,  21-27 
Strawberry  fruit,  73 
Successions  among  plant>5,  175 
Sun  leaves,  55 
Supplies,  dealers  in,  225,  226 

Taraxacum,  type  study,  186,  187 
Temperature,  effect  on  absorption  of 

water,  34,  35 
Tolypothrix,  type  study,  86 
Tomato  fruit,  71 
Transpiration,  60-63 
Trillium  flower,  64-6<J 
Tropjeolum  leaves,  starch  in,  67,  58 
Tropa'olum,  study  of,  16-17 
Tulip  flower,  ij(j,  67 


Ulothrix,  type  study,  89,  90 
Ulva,  type  study,  91 
Ustilago,  type  study,  114 

Vaucheria,  type  study,  94-96 
Vernation,  50 
Violacefe,  type  study,  185 
Volvox,  type  study,  88 

Water  cultures,  33,  34 

Water,  movementjof,  in  leaves,  68 

Water,  percentage  of,  in  j)lant  body, 

33 
Water,  rise  of,  34,  35,  45,  46,  63 
Windsor  beans,  36,  36 

Xerophytes,  176,  176 

Yeast,  culture  of,  105,  106 
Yeast,  type  study,  106 

Zonation,  177-179 

Zoiispores,  formation  and  habits  of, 
91 


ANNOUNCEMENTS 


BERGEN  AND  CALDWELL 
BOTANIES 

By  Joseph  Y.  Bergen  and  Otis  W.  Caldwkll,  The  University  of  Chicago 


INTRODUCTION    TO    BOTANY     368  pages,  illustrated       .    ?I.I5 

With  Key  and  Flora 140 

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The  Bergen  and  Caldwell  Botanies  have  been  received  with 
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V.  That  it  is  better  and  more  fully  illustrated  than  any  other  book 
for  beginners  in  botany. 

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from  the  book. 


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